CLAYMORE SECURITIES DEFINED PORTFOLIOS,
                                   SERIES 641

  CLAYMORE/GUGGENHEIM INTERMEDIATE INVESTMENT-GRADE CORPORATE TRUST, SERIES 17


                            REFERENCE TRUST AGREEMENT


   This Reference Trust Agreement dated as of January 28, 2010, between Claymore
Securities, Inc., as Depositor, and The Bank of New York Mellon, as Trustee,
sets forth certain provisions in full and incorporates other provisions by
reference to the document entitled "Standard Terms and Conditions of Trust For
Series Formed on or Subsequent to February 6, 2002" (herein called the "Standard
Terms and Conditions of Trust"), and such provisions as are set forth in full
and such provisions as are incorporated by reference constitute a single
instrument. All references herein to Articles and Sections are to Articles and
Sections of the Standard Terms and Conditions of Trust.

                                WITNESSETH THAT:

   In consideration of the premises and of the mutual agreements herein
contained, the Depositor and the Trustee agree as follows:

                                     PART I.

                     STANDARD TERMS AND CONDITIONS OF TRUST

   Subject to the provisions of Part II hereof, all the provisions contained in
the Standard Terms and Conditions of Trust are herein incorporated by reference
in their entirety and shall be deemed to be a part of this instrument as fully
and to the same extent as though said provisions had been set forth in this
instrument for each separate Trust created under this Series.

                                    PART II.

                      SPECIAL TERMS AND CONDITIONS OF TRUST

   The following special terms and conditions are hereby agreed to:

   (1) The securities listed in the Schedule(s) hereto have been deposited in
the Trust(s) under this Reference Trust Agreement as indicated on the attached
Schedule A.

   (2) For the purposes of the definition of the term "Unit" in Article I, it is
hereby specified that the fractional undivided interest in and ownership of a
Trust is the amount described in Amendment No. 2 to the Trust's Registration
Statement (Registration No. 333-162604) as filed with the Securities and
Exchange Commission today. The fractional undivided interest may (a increase by
the number of any additional Units issued pursuant to Section 2.05, (b) increase
or decrease in connection with an adjustment to the number of Units pursuant to
Section 2.05, or (c) decrease by the number of Units redeemed pursuant to
Section 5.02.

   (3) The term "Record Date" shall mean the dates set forth in the Prospectus
for principal distributions and interest distributions.

   (4) The term "Distribution Date" shall mean the dates set forth in the
Prospectus for principal distributions and interest distributions.

   (5) The term "Initial Date of Deposit" shall mean the date of this Reference
Trust Agreement as set forth above.

   (6) The number of Units of the Trust(s) referred to in Section 2.03 shall be
equal to the "Number of Units" in the Statement of Financial Condition in the
Prospectus.

   (7) Article I is hereby amended to add the following definitions:

   "Deferred Sales Charge" shall mean the deferred sales fee as described in the
Prospectus.

   (8) The definition of "Supplemental Indenture" is hereby deleted in its
entirety.

   (9) The definition of "Unitholder" is hereby amended as follows:

   "Unitholder" shall mean the registered holder of any Unit of beneficial
interest, his legal representative and heirs, or the successors of any
corporation, partnership or other legal entity and as such shall be deemed a
beneficiary of the related Trust created by this Indenture to the extent of his
pro rata share thereof.

   (10) Section 2.01 is hereby amended and replaced in its entirety as follows:

   Section 2.01. Deposit of Securities. The Depositor, on the date of the
Reference Trust Agreement, has deposited with the Trustee in trust the
Securities and contracts (or cash or a letter of credit in the amount necessary
to settle any contracts for the purchase of securities entered into by the
Trustee pursuant to the instructions of the Depositor) for the purchase of
Contract Securities listed under the "Trust Portfolio" in the Prospectus in
bearer form or duly endorsed in blank or accompanied by all necessary
instruments of assignment and transfer in proper form or Contract Securities
relating to such Securities to be held, managed and applied by the Trustee as
herein provided. The Depositor shall deliver the Securities listed in said
Prospectus which were not actually delivered concurrently with the execution and
delivery of the Reference Trust Agreement and which were represented by Contract
Securities to the Trustee within 10 calendar days after said execution and
delivery (the "Delivery Period"). In the event that the purchase of Contract
Securities pursuant to any contract shall not be consummated in accordance with
said contract or if the Securities represented by Contract Securities are not
delivered to a Trust in accordance with this Section 2.01 and the moneys, or, if
applicable, the moneys drawn on the Letter of Credit, deposited by the Depositor
are not utilized for Section 3.17 purchases of Replacement Bonds, such funds, to
the extent of the purchase price of failed Contract Securities for which no
Replacement Bonds were acquired pursuant to Section 3.17, plus all amounts
described in the next succeeding sentence, shall be credited to the Principal
Account and distributed pursuant to Section 3.06 to Unitholders of record as of
the Record Date next following the failure of consummation of such purchase. The
Depositor shall cause to be refunded to each Unitholder his pro rata portion of
the sales charge levied on the sale of Units to such Unitholder attributable to
such failed Contract Security. Any amounts remaining from moneys drawn on the
Letter of Credit which are not used to purchase Replacement Bonds or are not
used to provide refunds to Unitholders shall be paid to the Depositor. The
Trustee is hereby irrevocably authorized to effect registration or transfer of
the Securities in fully registered form to the name of the Trustee or to the
name of its nominee or to hold the Securities in a clearing agency registered
with the Securities and Exchange Commission or in a book entry system operated
by the Federal Reserve Board.

   (11) Section 2.03 is hereby amended and replaced in its entirety as follows:

   Section 2.03. Issuance of Units. By executing the Reference Trust Agreement
and receipt for deposited Securities, the Trustee will thereby acknowledge
receipt of the deposit of the Securities listed under the "Trust Portfolio" in
the Prospectus and referred to in Section 2.01 hereof, and simultaneously with
the receipt of said deposit, has recorded on its books, for each of the plans of
distribution provided for in the Prospectus, the ownership by the Depositor or
such other person or persons as may be indicated by the Depositor, of the
aggregate number of Units specified in the Prospectus and has delivered, or on
the order of the Depositor will deliver, in exchange for such Securities, cash
or a letter of credit, documentation evidencing the ownership of the number of
Units specified or, if requested by the Depositor, the ownership by the
Depository Trust Company ("DTC") of all such Units and will cause such Units to
be credited at DTC to the account of the Depositor or, pursuant to the
Depositor's direction and as hereafter provided, the account of the issuer of
the Letter of Credit referred to in Section 2.01. The number of Units in a Trust
may be increased through a split of the Units or decreased through a reverse
split thereof, as directed by the Depositor, on any day on which the Depositor
is the only Unitholder of such Trust, which revised number of Units shall be
recorded by the Trustee on its books. The Trustee hereby agrees that on the date
of any deposit of Additional Securities pursuant to Section 2.05 it shall
acknowledge that the Additional Securities identified therein have been
deposited with it by recording on its books the ownership, by the Depositor or
such other person or persons as may be indicated by the Depositor, of the
aggregate number of Units to be issued in respect of such Additional Securities
so deposited.

   Units shall be held solely in uncertificated form evidenced by appropriate
notation in the registration books of the Trustee, and no Unit holder shall be
entitled to the issuance of a Certificate evidencing the Units owned by such
Unit holder. The only permitted registered holders of Units shall be through the
DTC (or its nominee, Cede & Co.); consequently, individuals must hold their
Units through an entity which is a participant in DTC.

   (12) Section 2.05(a) is hereby amended and replaced in its entirety as
follows:

   Section 2.05. Deposit of Additional Securities. (a) Subject to the
requirements set forth below in this Section, the Depositor may, on any Business
Day (the "Trade Date"), subscribe for Additional Units as follows:

   (1) Prior to the Evaluation Time defined in Section 4.01 on the Trade Date,
the Depositor shall provide notice (the "Subscription Notice") to the Trustee,
by telephone or by written communication, of the Depositor's intention to
subscribe for Additional Units. The Subscription Notice shall identify the
Additional Securities to be acquired (unless such Additional Securities are a
precise replication of the then existing portfolio) and shall either (i) specify
the quantity of Additional Securities to be deposited by the Depositor on the
settlement date for such subscription or (ii) instruct the Trustee to purchase
Additional Securities with an aggregate cost as specified in the Subscription
Notice.

   (2) Promptly following the Evaluation Time on such Business Day, the
Depositor shall verify with the Trustee, the number of Additional Units to be
created.

   (3) Not later than the time on the settlement date for such subscription when
the Trustee is to deliver or assign the Additional Units created thereby, the
Depositor shall deposit with the Trustee (i) any Additional Securities specified
in the Subscription Notice (or contracts to purchase such Additional Securities
together with cash or a letter of credit in the amount necessary to settle such
contracts) or (ii) cash or a letter of credit in the amount equal to the
aggregate value of the Additional Securities to be purchased by the Trustee, as
specified in the Subscription Notice, together with, in each case, Cash as
defined below. "Cash" means, as to the Principal Account, cash or other property
(other than Securities) on hand in the Principal Account or receivable and to be
credited to the Principal Account as of the Evaluation Time on the Business Day
preceding the Trade Date (other than amounts to be distributed solely to persons
other than persons receiving the distribution from the Principal Account as
holders of Additional Units created by the deposit), and, as to the Interest
Account, interest received by the Trust as of the Evaluation Time on the
Business Day preceding the Trade Date or receivable by the Trust in respect of
interest or other distributions declared but not received as of the Evaluation
Time on the Business Day preceding the Trade Date, reduced by the amount of any
interest received or receivable on any Security allocable (in accordance with
the Trustee's calculation of the monthly distribution from the Interest Account
pursuant to Section 3.06) to a distribution made or to be made in respect of a
Record Date occurring prior to the Trade Date. Each deposit made pursuant to
this Section 2.05 shall replicate, to the extent practicable, the portfolio
immediately prior to such deposit.

   (4) On the settlement date for a subscription, the Trustee shall, in exchange
for the Securities and cash or Letter of Credit described above, issue and
deliver to or assign in the name of or on the order of the Depositor the number
of Units verified by the Depositor with the Trustee. No Unit to be issued
pursuant to this paragraph shall be issued or delivered unless and until
Securities, cash or a Letter of Credit is received in exchange therefor and no
person shall have any claim to any Unit not so issued and delivered or any
interest in the Trust in respect thereof.

   (5) Any Additional Securities shall be held, administered and applied by the
Trustee in the same manner as herein provided for the Securities.

   (6) The acceptance of Additional Units by the Depositor in accordance with
the provisions of paragraph (a) of this Section shall be deemed a certification
by the Depositor that the deposit or purchase of Additional Securities
associated therewith complies with the conditions of this Section 2.05.

   (7) Notwithstanding the preceding, in the event that the Depositor's
Subscription Notice shall instruct the Trustee to purchase Additional Securities
in an amount which, when added to the purchase amount of all other unsettled
contracts entered into by the Trustee, exceeds 25% of the value of the
Securities then held (taking into account the value of contracts to purchase
Securities only to the extent that there has been deposited with the Trustee
cash or an irrevocable letter of credit in an amount sufficient to settle their
purchase), the Depositors shall deposit with the Trustee concurrently with the
Subscription Notice cash or a letter of credit in an amount such that, when
added to 25% of the value of the Securities then held (determined as above) the
aggregate value shall be not less than the purchase amount of the securities to
be purchased pursuant to such Subscription Notice.

   (13) Section 3.01 is hereby amended as follows:

   Section 3.01. Initial Costs. Subject to reimbursement as hereinafter
provided, the cost of organizing the Trust and sale of the Trust Units shall be
borne by the Depositor, provided, however, that the liability on the part of the
Depositor under this Section shall not include any fees or other expenses
incurred in connection with the administration of the Trust subsequent to the
deposit referred to in Section 2.01. Upon notification from the Depositor that
the primary offering period is concluded, or after six months, at the discretion
of the Depositor, the Trustee shall withdraw from the Account or Accounts
specified in the Prospectus or, if no Account is therein specified, from the
Principal Account as further set forth in Section 3.04, and pay to the Depositor
the Depositor's reimbursable expenses of organizing the Trust and sale of the
Trust Units in an amount certified to the Trustee by the Depositor but not in
excess of the estimated per-Unit amount set forth in the Prospectus multiplied
by the number of Units outstanding as of the conclusion of such period. If the
cash balance of the Principal Account is insufficient to make such withdrawal,
the Trustee shall, as directed by the Depositor, sell Securities identified by
the Depositor, or distribute to the Depositor Securities having a value, as
determined under Section 4.01 as of the date of distribution, sufficient for
such reimbursement. The reimbursement provided for in this Section shall be for
the account of the Unitholders of record at the conclusion of the period
described above. Any assets deposited with the Trustee in respect of the
expenses reimbursable under this Section shall be held and administered as
assets of the Trust for all purposes hereunder. The Depositor shall deliver to
the Trustee any cash identified in the "Statement of Financial Condition" of the
Trust included in the Prospectus not later than the First Settlement Date and
the Depositor's obligation to make such delivery shall be secured by cash or the
Letter of Credit deposited pursuant to Section 2.01. Any cash which the
Depositor has identified as to be used for reimbursement of expenses pursuant to
this Section shall be held by the Trustee, without interest, and reserved for
such purpose and, accordingly, prior to the conclusion of the primary offering
period or after six months, at the discretion of the Depositor, shall not be
subject to distribution or, unless the Depositor otherwise directs, used for
payment of redemptions in excess of the per-Unit amount payable pursuant to the
next sentence. If a Unitholder redeems Units prior to the conclusion of the
primary offering period or after six months, at the discretion of the Depositor,
the Trustee shall pay to the Unitholder, in addition to the Redemption Price of
the tendered Units, an amount equal to the estimated per-Unit cost of organizing
the Trust and the sale of Trust Units set forth in the Prospectus multiplied by
the number of Units tendered for redemption; to the extent the cash on hand in
the Trust is insufficient for such payment, the Trustee shall have the power to
sell Securities in accordance with Section 5.02. As used herein, the Depositor's
reimbursable expenses of organizing the Trust and sale of the Trust Units shall
include the cost of the initial preparation and typesetting of the registration
statement, prospectuses (including preliminary prospectuses), the indenture, and
other documents relating to the Trust, Securities and Exchange Commission and
state blue sky registration fees, the cost of the initial valuation of the
portfolio and audit of the Trust, the costs of a portfolio consultant, the
initial fees and expenses of the Trustee, and legal and other out-of-pocket
expenses related thereto but not including the expenses incurred in the printing
of preliminary prospectuses and prospectuses, expenses incurred in the
preparation and printing of brochures and other advertising materials and any
other selling expenses.

   (14) Section 3.06(b)(ii) is hereby amended as follows:

   (ii) (a) For the purposes of this Section 3.06, the "Interest Distribution"
of a Unitholder shall be made on the basis of one-twelfth of the estimated
annual interest income to the Trust for the ensuing twelve months, after a
pro-rated initial payment and after deduction of the estimated costs and
expenses to be incurred on behalf of such Unitholders during the twelve month
period for which such interest income has been estimated.

   (b) In the event the amount on deposit in the Interest Account of any Trust
on a Distribution Date is not sufficient for the payment of the amount of
interest to be distributed monthly on the basis of the aforesaid computation,
the Trustee shall advance out of its own funds and cause to be deposited in and
credited to such Interest Account such amount as may be required to permit
payment of the monthly interest distribution to be made as described above and
shall be entitled to be reimbursed, without interest, out of interest received
by such Trust subsequent to the date of such advance and subject to the
condition that any such reimbursement shall be made only under conditions which
will not reduce the funds in or available for the Interest Account to an amount
less than required for the next ensuing distribution of interest. The Trustee's
fee takes into account the costs attributable to the outlay of capital needed to
make such advances. To the extent practicable, the Trustee shall allocate the
expenses of each Trust among Units of such Trust, giving effect within any Trust
to differences in administrative and operational cost among those who have
chosen to receive a particular plan of distribution is provided for in the
Prospectus.

   (c) Unitholders of any Trust desiring to receive according to a particular
plan of distribution provided for in the Prospectus may elect at the time of
purchase to receive distributions by notice to the Trustee. Unitholders must
furnish written notice to the Trustee indicating their desire to receive such
distributions. The Trustee, within five business days of receiving such notice,
shall issue to the Unitholder a confirmation indicating such Unitholder's
preferred distribution plan. Such notice shall be effective with respect to
subsequent distributions until changed by further notice to the Trustee. Those
wishing to change their plan of distribution, if multiple distribution plans are
provided for in the Prospectus, must do so by sending written notice at any time
to the Trustee. Changes may be made as soon as reasonably practicable.

   (15) Section 3.08(a)(x) is hereby amended as follows:

   (x) that as of any Record Date such Bonds are scheduled to be redeemed and
paid prior to the next succeeding monthly Distribution Date; provided, however,
that as the result of such sale the Trustee will receive funds in an amount
sufficient to enable the Trustee to include in the distribution from the
Principal Account on such next succeeding monthly Distribution Date at least
$1.00 per Unit; or

   (16) Section 4.01(b) is hereby amended and replaced in its entirety as
follows:

   (b) In making the evaluations the Evaluator may determine the value of each
issue of the Securities in each Trust by the following methods or any
combination thereof which it deems appropriate: (i) on the basis of current bid
or offering prices of such Securities as obtained from investment dealers or
brokers (including the Depositor) who customarily deal in public bonds
comparable to those held by the Trust, or (ii) if bid or offering prices are not
available for any of such Securities, on the basis of bid or offering prices for
comparable Securities, or (iii) by appraisal. The Evaluator may utilize a
securities pricing service to help determine the value of each issue so long as
such service uses a similar methodology to determine securities prices.
Securities prices for primary market purchases shall be based upon offering
prices of said Securities. Securities prices for redemptions shall be based on
bid prices of said Securities. In addition to the methods of determining the
value of the Securities described above, the Evaluator may make the initial
evaluation of Securities in whole or in part by reference to the Blue List of
Current Municipal Offerings (a daily publication containing the current public
offering prices of public bonds of all grades currently being offered by dealers
and banks).

   (17) The first paragraph of Section 5.01 is hereby amended and restated to
read as follows:

   Section 5.01. Trust Evaluation. As of the Evaluation Time (a) on the last
Business Day of each year, (b) on the day on which any Unit is tendered for
redemption and (c) on any other day desired by the Trustee or requested by the
Depositor, the Trustee shall: Add (i) all moneys on deposit in a Trust
(excluding (1) cash, cash equivalents or Letters of Credit deposited pursuant to
Section 2.01 hereof for the purchase of Contract Securities, unless such cash or
Letters of Credit have been deposited in the Interest and Principal Accounts
because of failure to apply such moneys to the purchase of Contract Securities
pursuant to the provisions of Sections 2.01, 3.03 and 3.04 hereof and (2) moneys
credited to the Reserve Account pursuant to Section 3.05 hereof), plus (ii) the
aggregate Evaluation of all Securities (including Contract Securities and
Reinvestment Securities) on deposit in such Trust as is determined by the
Evaluator (such evaluations shall take into account and itemize separately (i)
the cash on hand in the Trust or moneys in the process of being collected from
matured interest coupons or bonds matured or called for redemption prior to
maturity, (ii) the value of each issue of the Securities in the Trust on the bid
side of the market as determined by the Evaluator pursuant to Section 4.01, and
(iii) interest accrued thereon not subject to collection and distribution. For
each such Evaluation there shall be deducted from the sum of the above (i)
amounts representing any applicable taxes or governmental charges payable out of
the respective Trust and for which no deductions shall have previously been made
for the purpose of addition to the Reserve Account, (ii) amounts representing
estimated accrued fees of the Trust and expenses of such Trust including but not
limited to unpaid fees and expenses of the Trustee, the Evaluator, the
Supervisor, the Depositor and bond counsel, in each case as reported by the
Trustee to the Evaluator on or prior to the date of evaluation, (iii) any moneys
identified by the Trustee, as of the date of the Evaluation, as held for
distribution to Unitholders of record as of a Record Date or for payment of the
Redemption Value of Units tendered prior to such date and (iv) unpaid
organizational and offering costs in the estimated amount per Unit set forth in
the Prospectus. The resulting figure is herein called a "Trust Fund Evaluation."
The value of the pro rata share of each Unit of the respective Trust determined
on the basis of any such evaluation shall be referred to herein as the "Unit
Value."

   (18) Section 5.02 is hereby amended in its entirety as follows:

   Section 5.02. Redemptions by Trustee; Purchases by Depositor. Any Unit
tendered for redemption by a Unitholder or his duly authorized attorney to the
Trustee at its unit investment trust division office shall be redeemed by the
Trustee no later than the seventh calendar day following the day on which tender
for redemption is made in proper form, provided that if such day of payment is
not a Business Day, then such payment shall be made no later than the first
Business Day prior thereto (herein referred to as the "Settlement Date").
Unitholders must sign the request exactly as their name appears on the records
of the Trustee. If the amount of redemption is $500 or less and the proceeds are
payable to the Unitholders of record at the address of record, no signature
guarantee is necessary for redemptions by individual account owners (including
joint owners). Additional documentation may be requested, and a signature
guarantee is always required, from corporations, executors, administrators,
trustees, guardians and associations. The signatures must be guaranteed by a
participant in the Securities Transfer Agents Medallion Program (STAMP) or such
other signature guarantee program in addition to, or in substitution for, STAMP,
as may be accepted by the Trustee. Subject to (a) the next succeeding paragraph,
(b) payment by such Unitholder of any tax or other governmental charges which
may be imposed thereon and (c) payments in the form of In Kind Distributions (as
defined below), such redemption is to be made by payment of cash equivalent to
the Unit Value determined on the basis of a Trust Fund Evaluation made in
accordance with Section 5.01 determined by the Trustee as of the Evaluation Time
on the Redemption Date, multiplied by the number of Units tendered for
redemption (herein called the "Redemption Value"), or, if the Unitholder wishes
to redeem a number of Units less than all those so tendered, multiplied by the
number of Units so designated by such Unitholder for redemption. Units received
for redemption by the Trustee on any day after the Evaluation Time will be held
by the Trustee until the next day on which the New York Stock Exchange is open
for trading and will be deemed to have been tendered on such day for redemption
at the Redemption Value computed on that day.

   The portion of the Redemption Value which represents income shall be
withdrawn from the Principal Account to the extent available. The balance paid
on any Redemption Value, including income not paid from the Principal Account,
if any, shall be withdrawn from the Principal Account to the extent that funds
are available for such purpose. If such available funds shall be insufficient,
the Trustee shall sell such Securities as have been designated on the current
list for such purpose by the Supervisor (or by the Evaluator), as hereinafter in
this Section 5.02 provided, in amounts as the Trustee in its discretion shall
deem advisable or necessary in order to fund the Principal Account for purposes
of such redemption. Sale of Securities by the Trustee shall be made in such
manner as the Trustee shall determine will bring the best price obtainable for a
Trust, subject to any limitations as to the minimum amount of Securities to be
sold specified in the Reference Trust Agreement. In the event that either (i)
funds are withdrawn from the Principal Account and are applied to the payment of
income upon any redemption of Units or (ii) Securities are sold for the payment
of the Redemption value and any portion of the proceeds of such sale is applied
to the payment of income upon such redemption, then, in either such event, the
Principal Account shall be reimbursed therefor at such time as sufficient funds
may be next available in the Principal Account for such purpose.

   The Trustee may in its discretion, and shall when so directed by the
Depositor in writing, suspend the right of redemption for Units of a Trust or
postpone the date of payment of the Redemption Value for more than seven
calendar days following the day on which tender for redemption is made (i) for
any period during which the New York Stock Exchange is closed other than
customary weekend and holiday closings or during which (as determined by the
Securities and Exchange Commission) trading on the New York Stock Exchange is
restricted; (ii) for any period during which an emergency exists as a result of
which disposal of the Securities by the Trustee is not reasonably practicable or
it is not reasonably practicable fairly to determine in accordance herewith the
underlying value of the Securities; or (iii) for such other period as the
Securities and Exchange Commission may by order permit, and shall not be liable
to any person or in any way for any loss or damage which may result from any
such suspension or postponement.

   Not later than the close of business on the day of tender of any Unit for
redemption by a Unitholder other than the Depositor, the Trustee shall notify
the Depositor of such tender. The Depositor shall have the right to purchase
such Unit by notifying the Trustee of its election to make such purchase as soon
as practicable thereafter but in no event subsequent to the close of business on
the second succeeding Business Day after the day on which such Unit was tendered
for redemption. Such purchase shall be made by payment by the Depositor to the
Unitholder at the price so bid by making payment therefor to the Unitholder in
an amount not less than the Redemption Value on the day of tender not later than
the day on which the Units would otherwise have been redeemed by the Trustee to
such Unitholder. So long as the Depositor maintains a bid in the secondary
market, the Depositor may repurchase the Units tendered to the Trustee for
redemption by the Depositor but shall be under no obligation to maintain any
bids and may, at any time while so maintaining such bids, cease to do so
immediately at any time or from time to time without notice.

   Any Units so purchased by the Depositor may at the option of the Depositor be
tendered to the Trustee for redemption at the unit investment trust office of
the Trustee in the manner provided in the first paragraph of this Section 5.02.

   Notwithstanding the foregoing provisions of this Section 5.02, until the
close of business on the second Business Day after the day on which such Unit
was tendered for redemption, the Trustee is hereby irrevocably authorized in its
discretion, in the event that the Depositor does not purchase any Units tendered
to the Trustee for redemption, or in the event that a Unit is being tendered by
the Depositor for redemption, in lieu of redeeming Units, to sell Units in the
over-the-counter market through any broker-dealer of its choice for the account
of the tendering Unitholder at prices which will return to the Unitholder an
amount in cash, net after deducting brokerage commissions, transfer taxes and
other charges, equal to or in excess of the Redemption Value which such
Unitholder would otherwise be entitled to receive on redemption pursuant to this
Section 5.02. The Trustee shall pay to the Unitholder the net proceeds of any
such sale on the day on which such Unitholder would otherwise be entitled to
receive payment of the Redemption Value hereunder.

   Notwithstanding anything to the contrary in this Section 5.02, any Unitholder
may, if such Unitholder tenders at least that minimum amount of Units for
redemption specified in the Prospectus, request at the time of tender to receive
from the Trustee in lieu of cash such Unitholder's pro rata share of each
Security then held by such Trust; provided, however, if a Unitholder tenders for
redemption Units having an aggregate value of at least the amount specified in
the Prospectus, if any, the Depositor reserves the right to direct the Trustee
to make an In Kind Distribution rather than make a cash payment. Such tendering
Unitholder will receive his pro rata number of whole shares of each of the
Securities comprising the portfolio of such Trust and cash from the Principal
Account equal to the value of the fractional shares to which such tendering
Unitholder is entitled. Such pro rata share of each Security and the related
cash to which such tendering Unitholder is entitled is referred to herein as an
"In Kind Distribution." An In Kind Distribution will be made by the Trustee
through the distribution of each of the Securities in book-entry form to the
account of the Unitholder's bank or broker-dealer at DTC. If funds in the
Principal Account are insufficient to cover the required cash distribution to
the tendering Unitholder, the Trustee shall sell Securities according to the
criteria discussed herein. The Depositor may terminate the right of Unitholder
to make In-Kind Distributions at any time or from time to time without notice.

   The Supervisor shall maintain with the Trustee a current list of Securities
designated to be sold for the purpose of funding the Principal Account for
redemption of Units tendered for redemption and, to the extent necessary, for
payment of expenses under this Indenture. In connection therewith, the Depositor
may specify in the Prospectus and/or the Reference Trust Agreement the minimum
amounts of any Securities to be sold at any one time. If the Supervisor shall
for any reason fail to maintain such a list, the Trustee may in its sole
discretion designate a current list of Securities for such purposes. The net
proceeds of any sale of such Securities representing income shall be credited to
the Principal Account and then disbursed therefrom for payment of expenses and
payments to Unitholders required to be paid under this Indenture. Any balance
remaining after such disbursements shall remain credited to the Principal
Account.

   Neither the Depositor nor the Trustee shall be liable or responsible in any
way for depreciation or loss incurred by reason of any sale of Securities made
pursuant to this Section 5.02.

   Notwithstanding the foregoing, no In Kind Distribution requests made pursuant
to this Section 5.02 and submitted during the 30 business days prior to the
trust's Mandatory Termination Date will be honored. In addition, no unitholder
will be eligible for an In Kind Distribution of securities pursuant to Section
9.02. Furthermore, the availability of In Kind Distributions may be modified or
discontinued as described in the Prospectus.

   (19) The heading and the first sentence of Section 5.04 are hereby amended as
follows:

   Section 5.04. Units Held Through the Depository Trust Company or a Successor
Clearing Agency. No Unit may be registered in the name of any person other than
DTC or its nominee (or such other clearing agency registered as such pursuant to
Section 17A of the Exchange Act of 1934 designated as successor to DTC by the
Depositors, or the Trustee or the nominee thereof) (DTC and any such successor
clearing agency are herein referred to as the "Clearing Agency") unless the
Clearing Agency advises the Trustee that it is no longer willing or able
properly to discharge its responsibilities with respect to the Units and the
Trustee is unable to locate a qualified successor clearing agency, in which case
the Trustee shall notify the Clearing Agency and instruct it to provide the
Trustee with the name and address of all persons who are the beneficial owners
of Units as registered on the books of the Clearing Agency (the "Owners").

   (20) The second paragraph of Section 9.02 is hereby amended as follows:

   In the event of a termination, the Trustee shall proceed to liquidate the
Securities then held and make the payments and distributions provided for
hereinafter in this Section 9.02 based on such Unitholder's pro rata interest in
the balance of the Principal and Interest Accounts after the deductions herein
provided. Written notice shall be given by the Trustee in connection with any
termination to each Unitholder at his address appearing on the registration
books of the Trustee and in connection with a Mandatory Termination Date such
notice shall be given no later than 30 days before the Mandatory Termination
Date.

   (21) Subsection (d) of Section 9.02 is hereby amended as follows:

   (d) make final distributions from such Trust, as follows:

   (i) to each Unitholder receiving distribution in cash, such holder's pro rata
share of the cash balances of the Interest and Principal Accounts; and

   (ii) on the conditions set forth in Section 3.05 hereof, to all Unitholders,
their pro rata share of the balance of the Reserve Account.

   (22) The first sentence of the Introduction is hereby modified as follows:

   These Standard Terms and Conditions of Trust, effective February 6, 2002,
shall be applicable to certain Claymore Securities Defined Portfolios
established after the date of effectiveness hereof containing certain debt
obligations, as provided in this paragraph.

   (23) The definition of "Bonds" in Article I is hereby modified as follows:

   (3) "Bonds" shall mean such of the debt obligations, including "when issued"
and/or "regular way" contracts, if any, for the purchase of certain bonds, and
cash or a certified check or checks and/or an irrevocable letter or letters of
credit in the amount required for such purchase, deposited in irrevocable trust
and listed under the "Trust Portfolio" in the Prospectus, and any obligations
received in exchange, substitution or replacement for such obligations pursuant
to Sections 3.09 and 3.18 hereof, as may from time to time continue to be held
as a part of the Trust to which such Reference Trust Agreement relates.

   (24) The first paragraph of Section 3.17 is hereby amended and replaced with
the following:

   Section 3.17. Replacement Bonds. In the event that any Bond is not delivered
due to any occurrence, act or event beyond the control of the Depositor and of
the Trustee (such a Bond being herein called a "Special Bond"), the Depositor
may so certify to the Trustee and instruct the Trustee to purchase Replacement
Bonds which have been selected by the Depositor having a cost and an aggregate
principal amount not in excess of the cost and aggregate principal amount of the
Special Bonds not so delivered. To be eligible for inclusion in the Trust, the
Replacement Bonds which the Depositor selects must: (i) for Trusts containing
municipal bonds, yield current interest which is exempt from taxation for
federal income tax purposes and, if the Trust is a State Trust, exempt from
taxation under the personal income tax law of the particular state involved;
(ii) have a fixed maturity or disposition date comparable to the bonds replaced;
(iii) be purchased at a price that results in a yield to maturity and in a
current return, in each case as of the execution and delivery of the applicable
Reference Trust Agreement, which is approximately equivalent to the yield
maturity and current return of the Special Bonds which failed to be delivered
and for which the Replacement Bonds are substituted; (iv) be purchased within
twenty days after delivery of notice of the failed contract to the Trustee or to
the Depositor, whichever occurs first; (v) for an uninsured trust, be rated in
the category BBB or better or its equivalent by at least one national rating
organization and (vi) for an insured trust, be rated in the category AAA or its
equivalent by at least one national rating organization. Any Replacement Bonds
received by the Trustee shall be deposited hereunder and shall be subject to the
terms and conditions of this Indenture to the same extent as other Bonds
deposited hereunder. No such deposit of Replacement Bonds shall be made after
the earlier of (i) 90 days after the date of execution and delivery of the
applicable Reference Trust Agreement or (ii) the first Distribution Date to
occur after the date of execution and delivery of the applicable Reference Trust
Agreement.

   (25) Article III is hereby amended by adding the following Section 3.19:

   Section 3.19. Bookkeeping and Administrative Expenses. If so provided in the
Prospectus, as compensation for providing bookkeeping and other administrative
services of a character described in Section 26(a)(2)(C) of the Investment
Company Act of 1940 to the extent such services are in addition to, and do not
duplicate, the services to be provided hereunder by the Trustee or the Depositor
for providing supervisory services, the Depositor shall receive at the times
specified in Section 3.06, against a statement or statements therefore submitted
to the Trustee an aggregate annual fee in an amount which shall not exceed that
amount set forth in the Prospectus, calculated as specified in Section 3.06, but
in no event shall such compensation, when combined with all compensation
received from other series of the Trust or other unit investment trusts
sponsored by the Depositor or its affiliates for providing such bookkeeping and
administrative services in any calendar year exceed the aggregate cost to the
Depositor for providing such services to such unit investment trusts. Such
compensation may, from time to time, be adjusted provided that the total
adjustment upward does not, at the time of such adjustment, exceed the
percentage of the total increase, during the period from the Trust Agreement to
the date of any such increase, in consumer prices for services as measured by
the United States Department of Labor Consumer Price Index entitled "All
Services Less Rent of Shelter" or similar index as described under Section 3.18.
The consent or concurrence of any Unitholder hereunder shall not be required for
any such adjustment or increase. Such compensations shall be paid by the
Trustee, upon receipt of invoice therefore from the Depositor, upon which, as to
the cost incurred by the Depositor of providing services hereunder the Trustee
may rely, and shall be charged against the Interest and Principal Accounts as
specified in Section 3.06. The Trustee shall have no liability to any Unitholder
or other person for any payment made in good faith pursuant to this Section.

   If the cash balance in the Interest and Principal Accounts shall be
insufficient to provide for amounts payable pursuant to this Section 3.19, the
Trustee shall have the power to sell (1) Securities from the current list of
Securities designated to be sold pursuant to Section 5.02 hereof, or (2) if no
such Securities have been so designated, such Securities as the Trustee may see
fit to sell in its own discretion, and to apply the proceeds of any such sale in
payment of the amounts payable pursuant to this Section 3.19.

   Any moneys payable to the Depositor pursuant to this Section 3.19 shall be
secured by a prior lien on the Trust except that no such lien shall be prior to
any lien in favor of the Trustee under the provisions of Section 6.04.

   (26) Article III is hereby amended by adding the following Section 3.20:

   Section 3.20. Deferred Sales Charge. If the Reference Trust Agreement and/or
Prospectus related to a Trust specify a Deferred Sales Charge, the Trustee
shall, on the dates specified and as provided in such Prospectus, withdraw from
the Interest Account or Principal Account (as specified in such Prospectus), an
amount per Unit specified in such Prospectus and credit such amount to a
special, non-Trust account maintained by the Trustee out of which the deferred
sales charge will be distributed to the Depositor (the "Deferred Sales Charge
Account"). If the balance in the applicable Account is insufficient to make such
withdrawal, the Trustee shall, as directed by the Depositor, either advance
funds in an amount equal to the proposed withdrawal and be entitled to
reimbursement of such advance upon the deposit of additional moneys in the
applicable Account, and/or sell Securities and credit the proceeds thereof in
kind to the Deferred Sales Charge Account; provided, however, that the Trustee
shall not be required to advance an aggregate amount in excess of $15,000
pursuant to this Section 3.20. Such direction shall, if the Trustee is directed
to sell a Security, identify the Security to be sold or distributed in kind and
include instructions as to the execution of such sale. If a Unitholder redeems
Units prior to full payment of the deferred sales charge, the Trustee shall, if
so provided in the related Prospectus, on the Redemption Date, withhold from the
Redemption Price payable to such Unitholder an amount equal to the unpaid
portion of the deferred sales charge and distribute such amount to the Deferred
Sales Charge Account or, if pursuant to Section 5.02 hereof, the Depositor shall
purchase a Unit tendered for redemption prior to the payment in full of the
deferred sales charge due on the tendered Unit, the Depositor shall pay to the
Unitholder the amount specified under Section 5.02 less the unpaid portion of
the deferred sales charge. All advances made by the Trustee pursuant to this
Section shall be secured by a lien on the Trust prior to the interest of the
Unitholders. If the Prospectus provides for a waiver or refund of any portion of
the deferred sales charge under specified circumstances (such as, for example,
in connection with a redemption or sale of Units following the death or
disability of the Unitholder), the Trustee shall deduct and pay to the Depositor
the full amount of the deferred sales charge chargeable upon the redemption in
the absence of such waiver or refund and the Depositor shall pay to the affected
Unitholder the amount of such waiver or refund; the Trustee shall have no
responsibility to the affected Unitholder with respect to the amount to be so
refunded. The Depositor may at any time instruct the Trustee to distribute to
the Depositor cash or Securities previously credited to the Deferred Sales
Charge Account. The Depositor represents that the price paid by any Unitholder
for Units acquired through reinvestment of Trust distributions will be reduced
by the aggregate amount of unpaid deferred sales charge at the time of the
purchase such that the subsequent collection by the Depositor of the deferred
sales charge in respect of the Units so acquired will be permissible under
applicable Financial Industry Regulatory Authority (FINRA) rules.

   (27) Section 7.05 is hereby amended in its entirety as follows:

   Section 7.05. Compensation. The Depositor shall receive at the times set
forth in Sections 3.06 and 3.18 as compensation for performing portfolio
supervisory services, 3.06 and 3.19 as compensation for performing bookkeeping
and administrative services and Sections 3.06 and 4.03 as compensation for
performing evaluation services, such amount and for such periods as specified in
the Prospectus and/or Reference Trust Agreement. The computation of such
compensation for performing portfolio supervisory services and bookkeeping and
administrative services shall be made on the basis of the largest number of
Units outstanding at any time during the period for which such compensation is
being computed. The compensation for performing evaluation services shall be
made on the basis of the principal amount of Bonds in such Trust on a monthly
basis. At no time, however, will the total amount received by the Depositor for
services rendered to all series of Claymore Securities Defined Portfolios in any
calendar year exceed the aggregate cost to them of supplying such services in
such year. Such rate may be increased by the Trustee from time to time, without
the consent or approval of any Unitholder, or the Depositor, by amounts not
exceeding the proportionate increase during the period from the date of such
Prospectus and/or Reference Trust Agreement to the date of any such increase, in
consumer prices as published either under the classification "All Services Less
Rent" in the Consumer Price Index published by the United States Department of
Labor or, if such Index is no longer published, a similar index.

   In the event that any amount of the compensation paid to the Depositor
pursuant to Sections 3.06, 3.18 and 3.19 is found to be an improper charge
against the Trust, the Depositor shall reimburse the Trust in such amount. An
improper charge shall be established if a final judgment or order for
reimbursement of the Trust shall be rendered against the Depositor and such
judgment or order shall not be effectively stated or a final settlement is
established in which the Depositor agrees to reimburse the Trust for amounts
paid to the Depositor pursuant to this Section 7.05.

   The Depositor may employ agents in connection with its duties referenced in
Section 7.05 and shall not be answerable for the default or misconduct of such
agents if they shall have been selected with reasonable care. The fees of such
agents shall be reimbursable to the Depositor from the Trust, provided, however,
that the amount of such reimbursement in any year (i) shall reduce the amount
payable to the Depositor for such year with respect to the service in question
and shall not exceed the maximum amount payable to the Depositor for such
service for such year and (ii) if such agent is an affiliate of the Depositor,
the amount of the reimbursement, when combined with (a) all compensation
received by such agent form other series of the Trust or other unit investment
trusts sponsored by the Depositor or its affiliates and (b) the amount payable
to the Depositor from the Trust and from other series of the Trust or other unit
investment trusts sponsored by the Depositor or its affiliates in respect of the
service in question, shall not exceed the aggregate cost of such agent and the
Depositor of providing such service. The Trustee shall pay such reimbursement
against the Depositor's invoice therefore upon which the Trustee may rely as the
Depositor's certification that the amount claimed complies with the provisions
of this paragraph.

   (28) Section 9.05 is hereby revised to read as follows:

   Section 9.05. Written Notice. Any notice, demand, direction or instruction to
be given to the Depositor, Evaluator or Supervisor hereunder shall be in writing
and shall be duly given if mailed or delivered to the Depositor, 2455 Corporate
West Drive, Lisle, Illinois 60532, or at such other address as shall be
specified by the Depositor to the other parties hereto in writing.

   Any notice, demand, direction or instruction to be given to the Trustee shall
be in writing and shall be duly given if delivered to the unit investment trust
division office of the Trustee at 2 Hanson Place, 12th Fl., Brooklyn, New York
11217, Attention: Unit Trust Division, or to such other address as shall be
specified by the Trustee to the other parties in writing.

   (29) The second paragraph of Section 6.02 is replaced in its entirety as
follows:

   An audit of the accounts of each Trust shall not be conducted unless the
Depositor determines that such an audit is required. In the event that the
Depositor determines that an audit is required, the accounts of each Trust shall
be audited not less than annually by independent public accountants designated
from time to time by the Depositor and reports of such accountants shall be
furnished by the Trustee, upon request, to Unitholders. The Trustee, however, in
connection with any such audits shall not be obligated to use Trust assets to
pay for such audits in excess of the amounts, if any, indicated in the
Prospectus relating to such Trust. The Trustee shall maintain and provide, upon
the request of a Unitholder or the Depositor, the Unitholders' or the
Unitholder's designated representative with the costs basis of the Securities
represented by the Unitholder's Units.

   (30) Article III is hereby amended by adding the following Section 3.21:

   Section 3.21. Creation and Development Fee. If the Prospectus related to a
Trust specifies a creation and development fee, the Trustee shall, on or
immediately after the end of the initial offering period, withdraw from the
Principal Account, an amount equal to the unpaid creation and development fee as
of such date and credit such amount to a special non-Trust account designated by
the Depositor out of which the creation and development fee will be distributed
to the Depositor (the "Creation and Development Account"). The creation and
development fee is the per unit amount specified in the Prospectus for the
Trust. If the balance in the Principal Account is insufficient to make such
withdrawal, the Trustee shall, as directed by the Depositor, advance funds in an
amount required to fund the proposed withdrawal and be entitled to reimbursement
of such advance upon the deposit of additional moneys in the Principal Account,
and/or sell Securities and credit the proceeds thereof to the Creation and
Development Account. Such direction shall, if the Trustee is directed to sell a
Security, identify the Security to be sold and include instructions as to the
execution of such sale. In the absence of such direction by the Depositor, the
Trustee shall sell Securities sufficient to pay the creation and development fee
(and any unreimbursed advance then outstanding) in full, and shall select
Securities to be sold in such manner as will maintain (to the extent
practicable) the relative proportion of number of shares of each Security then
held. The proceeds of such sales, less any amounts paid to the Trustee in
reimbursement of its advances, shall be credited to the Creation and Development
Account. If the Trust is terminated pursuant to Section 9.02, the Depositor
agrees to reimburse Unitholders for any amounts of the Creation and Development
Fee collected by the Depositor to which it is not entitled. All advances made by
the Trustee pursuant to this Section shall be secured by a lien on the Trust
prior to the interest of Unitholders. Notwithstanding the foregoing, the
Depositor shall not receive any amount of Creation and Development Fee which,
when added to any other sales charge imposed, exceeds the maximum amount per
Unit stated in the Prospectus. The Depositor shall notify the Trustee, not later
than ten business days prior to the date on which it anticipates that the
maximum amount of Creation and Development Fee it may receive has been accrued
and shall also notify the Trustee as of the date when the maximum amount of
Creation and Development Fee has been accrued. The Trustee shall have no
responsibility or liability for damages or loss resulting from any error in the
information in the preceding sentence. The Depositor agrees to reimburse the
Trust and any Unitholder any amount of Creation and Development Fee it receives
which exceeds the amount which the Depositor may receive under applicable laws,
regulations and rules.

   (31) Article III is hereby amended by adding the following Section 3.22:

   Section 3.22. License Fees. If so provided in the Prospectus, the Depositor
may enter into a Licensing Agreement (the "Agreement") with a licensor (the
"Licensor") described in the Prospectus in which the Trust(s), as consideration
for the licenses granted by the Licensor for the right to use its trademarks and
trade names, intellectual property rights or for the use of databases and
research owned by the Licensor, will pay a fee set forth in the Agreement to the
applicable Licensor or the Depositor to reimburse the Depositor for payment of
the expenses.

   If the Agreement provides for an annual license fee computed in whole or part
by reference to the average daily net asset value of the Trust assets, for
purpose of calculating the accrual of estimated expenses such annual fee shall
accrue at a daily rate and the Trustee is authorized to compute an estimated
license fee payment (i) until the Depositor has informed the Trustee that there
will be no further deposits of Additional Securities, by reference to an
estimate of the average daily net asset value of the Trust assets which the
Depositor shall provide the Trustee, (ii) thereafter and during the calendar
quarter in which the last business day of the period described in clause (i)
occurs, by reference to the net asset value of the Trust assets as of such last
business day, and (iii) during each subsequent calendar quarter, by reference to
the net asset value of the Trust assets as of the last business day of the
preceding calendar quarter. The Trustee shall adjust the net asset value (Trust
Fund Evaluation) as of the dates specified in the preceding sentence to account
for any variation between accrual of estimated license fee and the license fee
payable pursuant to the Agreement, but such adjustment shall not affect
calculations made prior thereto and no adjustment shall be made in respect
thereof.

   (32) Section 3.06 is hereby amended by adding the following subsection (c):

   (c) Notwithstanding the foregoing, if a Trust has elected to be treated as a
"regulated investment company" as defined in the Internal Revenue Code, the
Trustee may make such additional distributions to Unitholders as shall be
determined by the Depositor or such agent as the Depositor shall designate to be
necessary or desirable to maintain the status of each Trust as a regulated
investment company or to avoid imposition of any income or excise taxes on
undistributed income of the Trust. The Trustee shall be authorized to rely
conclusively upon the direction, and shall have no duty to make any additional
distributions from a Trust in the absence of such direction. The Trustee shall
have no liability for any tax or other liability incurred by reason of action or
inaction resulting from such direction. The fees of such agent designated by the
Depositor shall be an expense of the Trust reimbursable to the Trustee in
accordance with Section 7.05.

   (33) Section 9.01(a)(iii) is hereby amended as follows:

   (a)(iii) to make such other provision regarding matters or questions arising
hereunder as shall not materially adversely affect the interests of the
Unitholders; provided, however, that in no event may any amendment be made which
would adversely affect the status of a Trust for federal income tax purposes.

   (34) Section 9.01 is hereby amended by adding the following subsection (d):

   (d) If a Trust has elected to be treated as a "regulated investment company"
as defined in the Internal Revenue Code and notwithstanding Section 9.01(a),
this Indenture may be amended from time to time by the Depositor and the Trustee
without the consent of any of the Unitholders (1) to cure any ambiguity or to
correct or supplement any provisions contained herein which may be defective or
inconsistent with any other provision contained herein; (2) to change any
provision hereof as may be required by the Securities and Exchange Commission or
any successor governmental agency exercising similar authority; (3) to make such
amendments as may be necessary for each Trust to continue to qualify as a
regulated investment company for federal income tax purposes; or (4) to make
such other provisions in regard to matters or questions arising hereunder as
shall not materially adversely affect the interest of the Unitholders (as
determined in good faith by the Depositor and the Trustee). This Indenture may
also be amended from time to time by the Depositor and the Trustee (or the
performance of any of the provisions of this Indenture may be waived) with the
consent of holders of Units representing 66-2/3% of the Units at the time
outstanding under the Trust Indenture of the individual Trust or Trusts affected
for the purpose of adding any provisions of this Indenture or of materially
modifying in any manner the rights of the holders of Units of such Trust or
Trusts; provided, however, that in no event may any amendment be made which
would (1) alter the rights to the Unitholders as against each other, (2) provide
the Trustee with the power to engage in business or investment activities other
than as specifically provided in this Indenture or (3) adversely affect the
characterization of a Trust as a regulated investment company for federal income
tax purposes; provided, further, that the consent of 100% of the Unitholders of
any individual Trust is required to amend this Indenture (1) to reduce the
aforesaid percentage of Units the holders of which are required to consent to
certain amendments and (2) to reduce the interest in such Trust represented by
any Units of such Trust.

   Promptly after the execution of any amendment requiring the consent of the
Unitholders or any of any other amendment if directed by the Depositor, the
Trustee shall furnish written notification of the substance of such amendment to
each Unitholder then of record affected thereby.

   It shall not be necessary for the consent of Unitholders under this Section
9.01 or under Section 9.02 to approve the particular form of any proposed
amendment, but it shall be sufficient if such consent shall approve the
substance thereof. The manner of obtaining such consents and of evidencing the
authorization of the execution thereof by Unitholders shall be subject to such
reasonable regulations as the Trustee may prescribe.

   (35) Section 3.15 is hereby deleted and replaced in its entirety with the
following:

   Section 3.15. Regulated Investment Company Election. If so provided in the
Prospectus for a Trust, such Trust elects to be treated and to qualify as a
"regulated investment company" as defined in the Internal Revenue Code, and the
Trustee is hereby directed to make such elections, including any appropriate
election to be taxed as a corporation, as shall be necessary to effect such
qualification. In addition, the Trustee is authorized to take any actions
necessary to allow a Trust Fund to qualify as a regulated investment company.

   (36) Sections 3.08(a)(xii) and 3.08(a)(xiii are hereby deleted and replaced
as follows:

   (viii) that the sale of Bonds is necessary or advisable: (i) in order to
maintain the qualification of the Trust as a regulated investment company; or
(ii) to provide funds to make any distribution for a taxable year in order to
avoid imposition of any income or excise taxes on undistributed income in the
Trust; or

   (ix) the Depositor or its designee determines that such sale is appropriate.

   (37) All references to The Bank of New York in the Standard Terms and
Conditions of the Trust shall be replaced with "The Bank of New York Mellon."

   (38) Section 3.06(a) is deleted in its entirety and replaced with the
following:

   Section 3.06. Payments and Distributions. (a) On or immediately after the
fifteenth the day of each month, the Trustee shall satisfy itself as to the
adequacy of the Reserve Account, making any further credits thereto as may
appear appropriate in accordance with Section 3.05 and shall then with respect
to each Trust:

   (i) deduct from the Interest Account or, to the extent funds are not
available in such Account, from the Principal Account and pay to itself
individually the amounts that it is at the time entitled to receive pursuant to
Section 6.04 or otherwise pursuant to the provisions hereof;

   (ii) deduct from the Interest Account of the Trust, and, to the extent funds
are not sufficient therein, from the Principal Account of the Trust, amounts
necessary to pay any unpaid expenses of the Trust, including registration
charges, state blue sky fees, printing costs, attorneys' fees, auditing costs
and other miscellaneous out-of-pocket expenses, as certified by the Depositor,
incurred in keeping the registration of the Units and the Trust on a current
basis pursuant to Section 9.04, provided, however, that no portion of such
amount shall be deducted or paid unless the payment thereof from the Trust is at
that time lawful;

   (iii) deduct from the Interest Account or, to the extent funds are not
available in such Account, from the Principal Account and pay to, or reserve
for, the Supervisor the amount that it is at the time entitled to receive
pursuant to Section 3.18;

   (iv) deduct from the Interest Account or, to the extent funds are not
available in such Account, from the Principal Account and pay to, or reserve
for, the Evaluator the amount that it is at the time entitled to receive
pursuant to Section 4.03;

   (v) deduct from the Interest Account or, to the extent funds are not
available in such Account, from the Principal Account and pay to, or reserve
for, the Depositor the amount that it is at the time entitled to receive
pursuant to Section 3.19;

   (vi) deduct from the Interest Account or, to the extent funds are not
available in such Account, from the Principal Account and pay to counsel, as
hereinafter provided for, an amount equal to unpaid fees and expenses, if any,
of such counsel pursuant to Section 3.10, as certified to by the Depositor;

   (vii) deduct from the Interest Account or, to the extent funds are not
available in such Account, from the Principal Account, and reimburse itself for
any other fees, charges and expenses arising from time to time out of the Trust
operations that the Trustee has paid.

   (39) The first sentence of Section 3.06(b)(i) is hereby deleted and replaced
with the following:

   (b) (i) On each Distribution Date, the Trustee shall distribute an amount per
Unit equal to such Unitholder's Interest Distribution (as defined below)
computed as of the close of business on the Record Date immediately preceding
such Distribution Date to each Unitholder of record at the close of business on
the Record Date. In addition, if the balance of the Principal Account of a Trust
on the fifteenth day of any month equals at least $1.00 per Unit then
outstanding, such distribution from the Principal Account shall be made on the
twenty-fifth day of such month computed as of the close of business on the
fifteenth day of such month.

   (40) Notwithstanding anything to the contrary in the Standard Terms and
Conditions of the Trust, Section 3.19 is hereby amended by adding the following
paragraph:

   In limited circumstances and only if deemed in the best interests of the
Unitholders, the Depositor is authorized to instruct the Trustee to change the
dates on which the deferred sales charge is deducted as described in the
Prospectus. The deferred sales charge payment dates may be delayed: (i) in order
for a Trust which is a widely held fixed investment trust as defined in Treas.
Reg. Section 1.671-5(b)(22) to report in accordance with any of the safe harbor
methods described in Treas. Reg. Section 1.671-5(f); or (ii) in order for a
Trust which is a regulated investment company as defined by the Internal Revenue
Code to maintain its qualification as a regulated investment company. The
Trustee shall have no liability for any tax or other liability incurred by
reason of action or inaction resulting from such direction. The Depositor will
amend the Prospectus to include the new dates on which the deferred sales charge
will be collected and distributing such notice to Unitholders.

   This Reference Trust Agreement shall be deemed effective when executed and
delivered by the Sponsor and the Trustee.

   IN WITNESS WHEREOF, the parties hereto have caused this Reference Trust
Agreement to be duly executed.


                      CLAYMORE SECURITIES, INC., DEPOSITOR

                              By /s/ Kevin Robinson
             -------------------------------------------------------
                  Senior Managing Director, General Counsel and
                                    Secretary


                      THE BANK OF NEW YORK MELLON, TRUSTEE

                              By /s/ Thomas Balbone
             -------------------------------------------------------
                                 Vice President



                                   SCHEDULE A

                         SECURITIES INITIALLY DEPOSITED

               CLAYMORE SECURITIES DEFINED PORTFOLIOS, SERIES 641

  (Note: Incorporated herein and made a part hereof is the "Trust Portfolio(s)"
                        as set forth in the Prospectus.)