SC 13D/A

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934
(Amendment No. 1)*

TriMas Corporation

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

896215209

(CUSIP Number)

Daniel P. Tredwell

Heartland Industrial Associates L.L.C.

177 Broad Street, 10th Floor

Stamford, Connecticut 06901

(203) 327-1202

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

Copies to:

Charles J. Downey III, Esq.

Finn Dixon & Herling LLP

177 Broad Street, 15th Floor

Stamford, Connecticut 06901-2048

(203) 325-5000

November 30, 2009

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.12d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box o.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See § 240.13d-7 for other parties to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No.   896215209
	1.	Names of Reporting Persons Heartland Industrial Associates L.L.C.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 15,237,996 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 15,237,996 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 15,237,996 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 45.4%
	14.	Type of Reporting Person OO

2

CUSIP No.   896215209
	1.	Names of Reporting Persons Heartland Industrial Partners, L.P.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 14,186,057 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 14,186,057 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 14,186,057 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 42.2%
	14.	Type of Reporting Person PN

3

CUSIP No.   896215209
	1.	Names of Reporting Persons TriMas Investment Fund I, L.L.C.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 11,942,230 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 11,942,230 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 11,942,230 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 35.6%
	14.	Type of Reporting Person OO

4

CUSIP No.   896215209
	1.	Names of Reporting Persons Metaldyne Investment Fund I, L.L.C.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 2,243,827 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 2,243,827 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 2,243,827 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 6.7%
	14.	Type of Reporting Person OO

5

CUSIP No.   896215209
	1.	Names of Reporting Persons HIP Side-by-Side Partners, L.P.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 842,675 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 842,675 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 842,675 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 2.5%
	14.	Type of Reporting Person PN

6

CUSIP No.   896215209
	1.	Names of Reporting Persons TriMas Investment Fund II, L.L.C.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 176,312 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 176,312 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 176,312 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 0.5%
	14.	Type of Reporting Person OO

7

CUSIP No.   896215209
	1.	Names of Reporting Persons Metaldyne Investment Fund II, L.L.C.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 32,952 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 32,952 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 32,952 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 0.1%
	14.	Type of Reporting Person OO

8

CUSIP No.   896215209
	1.	Names of Reporting Persons HIP Side-by-Side I-A, L.L.C.
	2.	Check the Appropriate Box if a Member of a Group
		(a)			o
		(b)			x
	3.	SEC Use Only
	4.	Source of Funds WC
	5.	Check Box if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e)  o
	6.	Citizenship or Place of Organization Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:			7.	Sole Voting Power 0 Shares of Common Stock
			8.	Shared Voting Power 0 Shares of Common Stock
			9.	Sole Dispositive Power 0 Shares of Common Stock
			10.	Shared Dispositive Power 0 Shares of Common Stock
	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 0 Shares of Common Stock
	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructionso
	13.	Percent of Class Represented by Amount in Row (11) 0.0%
	14.	Type of Reporting Person OO

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Amendment No. 1 to Statement on Schedule 13D

This Amendment (this “Amendment”) No. 1 to Statement on Schedule 13D (the “Statement”) relates to the beneficial ownership of common stock, par value $0.01 per share (the “Common Stock”), of TriMas Corporation, a Delaware corporation (the “Issuer”).  This Amendment is being filed on behalf of the Reporting Persons.

The Reporting Persons are filing this Amendment to amend the statements on Schedule 13D with respect to the Common Stock filed with the Securities and Exchange Commission on March 20, 2009 pursuant to Rule 13d-1(d).

This Amendment is being filed by the Reporting Persons solely as a result of the termination of the Rule 10b5-1 Purchase Plan (as defined below) by the Purchasing Parties (as defined below).

Item 1. Security and Issuer.

(a)	Name of Issuer: TriMas Corporation
(b)	Address of Issuer’s Principal Executive Offices: 39400 Woodward Avenue, Suite 130 Bloomfield Hills, Michigan 48304
(c)	Title and Class of Securities:Common Stock, par value $0.01

Item 2.	Identity and Background.
No material change.
Item 3.	Source and Amount of Funds or Other Consideration.
No material change.
Item 4.	Purpose of Transaction.

Item 4 is hereby amended and restated to read in its entirety as follows:

On November 30, 2009, TIF I, TIF II, HIP Side-by-Side and HIP Side-by-Side I-A (collectively, the “Purchasing Parties”) terminated the Rule 10b5-1 Purchase Instruction (the “10b5-1 Purchase Plan”) with Credit Suisse Securities (USA) LLC (“Credit Suisse”).  No shares were purchased pursuant to the 10b5-1 Purchase Plan within the past 60 days.  The Purchasing Parties terminated the 10b5-1 Purchase Plan because the market price of the Common Stock has not been in the applicable price range under the 10b5-1 Purchase Plan since April 2009.  The last purchase under the 10b5-1 Purchase Plan was made on April 21, 2009.

Except as set forth above, although the Reporting Persons have no specific plan or proposal to acquire or dispose of Common Stock or other securities of the Issuer, consistent with their investment

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purpose, the Reporting Persons, at any time and from time to time, may acquire additional Common Stock or dispose of any or all of their Common Stock or other securities of the Issuer depending upon an ongoing evaluation of the investment in the Common Stock, prevailing market conditions, other investment opportunities, liquidity requirements of the Reporting Persons, and/or other investment considerations.

Also, consistent with the investment purpose, the Reporting Persons may engage in communications with one or more shareholders of the Issuer, one or more officers or employees of the Issuer, one or more members of the board of directors of the Issuer and/or one or more representatives of the Issuer regarding the Issuer, including but not limited to its operations, business, results, plans, prospects, ownership structure and management. The Reporting Persons may discuss ideas that, if effected, may result in acquisitions by persons of additional securities of the Issuer, an extraordinary corporate transaction involving the Issuer, changes in the Issuer’s capitalization and/or changes in the board of directors or management of the Issuer.

Except as set forth in this Statement, the Reporting Persons have no plans or proposals which relate to, or could result in, any of the matters referred to in paragraphs (a) through (j), inclusive, of the instructions to Item 4 of Schedule 13D. The Reporting Persons may, at any time and from time to time, review or reconsider their position and/or change their purpose and/or formulate plans or proposals with respect thereto.

Item 5. Interest in Securities of the Issuer.

(a)The approximate percentages of shares of Common Stock reported as beneficially owned by the Reporting Persons is based upon 33,578,324 shares of Common Stock outstanding as of November 9, 2009, as reported by the Issuer in its Quarterly Report on Form 10-Q for the quarter ended September 30, 2009 (as filed with the Securities and Exchange Commission on November 9, 2009).

As of the date hereof:

·11,942,230 shares of Common Stock are owned directly by TIF I;

·2,243,827 shares of Common Stock are owned directly by MIF I;

·842,675 shares of Common Stock are owned directly by HIP Side-by-Side;

·176,312 shares of Common Stock are owned directly by TIF II;

·32,952 shares of Common Stock are owned directly by MIF II; and

·no shares of Common Stock are owned directly by HIP Side-by-Side I-A (TIF I, MIF I, HIP Side-by-Side, TIF II, MIF II, and HIP Side-by-Side I-A, collectively, the “Direct Holders”).

HIP, as the managing member of TIF I and MIF I, is an indirect beneficial owner of shares held by TIF I and MIF I.  Associates, as the managing member of TIF II, MIF II and HIP Side-by-Side I-A, and the general partner of HIP and HIP Side-by-Side, is an indirect beneficial owner of the shares held by the Direct Holders.

(b)Please see Items 7, 8, 9, 10, 11, and 13 for each cover sheet for each Reporting Person.  Neither the present filing nor anything contained in this item 5 shall be construed as an admission that any combination of Reporting Persons constitutes a “group” for any purpose, and each Reporting Person disclaims beneficial ownership of securities held by each other Reporting Person.

(c)Except as set forth in Item 4 above, none of the Reporting Persons has effected any

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transaction in the Common Stock during the past 60 days.

(d)Except as set forth in this Item 5, no person other than each respective record owner referred to herein of securities is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities.

(e)Not applicable.

Item 6.	Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer
Item 6 is hereby amended by the addition of the following sentence to be added at the end thereof: “The Purchasing Parties terminated the 10b5-1 Purchase Plan on November 30, 2009.”
Item 7.	Exhibits

Exhibit A	Joint Filing Agreement, dated December 1, 2009, among the Reporting Persons (filed herewith).
Exhibit B	Amended and Restated Shareholders Agreement, dated as of July 19, 2002, by and among the Issuer and Metaldyne Corporation, as amended by Amendment No. 1 to the Amended and Restated Shareholders Agreement dated August 31, 2006 (incorporated herein by reference to Exhibits 10.2 and 10.3 to the Issuer’s Current Annual Report on Form 10-K, filed on March 10, 2009).
Exhibit C	Advisory Agreement, dated June 6, 2002, between HIP and the Issuer, as amended by the First Amendment to the Advisory Agreement dated November 1, 2006 between Associates and the Issuer, and as further amended by the Second Amendment to the Advisory Agreement dated November 1, 2006 between Associates and the Issuer (incorporated herein by reference to Exhibits 10.30, 10.31 and 10.32 to the Issuer’s Current Annual Report on Form 10-K, filed on March 10, 2009).

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Signature

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated:  December 1, 2009

HEARTLAND INDUSTRIAL ASSOCIATES L.L.C.
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member
HEARTLAND INDUSTRIAL PARTNERS, L.P.
By: Heartland Industrial Associates L.L.C., its General Partner
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member
TRIMAS INVESTMENT FUND I, L.L.C.
By: Heartland Industrial Associates L.L.C., the General Partner of Heartland Industrial Partners, L.P., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member
METALDYNE INVESTMENT FUND I, L.L.C.
By: Heartland Industrial Associates L.L.C., the General Partner of Heartland Industrial Partners, L.P., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member

13

HIP SIDE-BY-SIDE PARTNERS, L.P.
By: Heartland Industrial Associates L.L.C., its General Partner
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member
TRIMAS INVESTMENT FUND II, L.L.C.
By: Heartland Industrial Associates L.L.C., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member
METALDYNE INVESTMENT FUND II, L.L.C.
By: Heartland Industrial Associates L.L.C., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member
HIP SIDE-BY-SIDE I-A, L.L.C.
By: Heartland Industrial Associates L.L.C., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name: Daniel P. Tredwell
	Title: Managing Member

14

INDEX TO EXHIBITS

EXHIBIT A	Joint Filing Agreement, dated December 1, 2009, among the Reporting Persons (filed herewith).
EXHIBIT B	Amended and Restated Shareholders Agreement, dated as of July 19, 2002, by and among the Issuer and Metaldyne Corporation, as amended by Amendment No. 1 to the Amended and Restated Shareholders Agreement dated August 31, 2006 (incorporated herein by reference to Exhibits 10.2 and 10.3 to the Issuer’s Current Annual Report on Form 10-K, filed on March 10, 2009).
EXHIBIT C	Advisory Agreement, dated June 6, 2002, between HIP and the Issuer, as amended by the First Amendment to the Advisory Agreement dated November 1, 2006 between Associates and the Issuer, and as further amended by the Second Amendment to the Advisory Agreement dated November 1, 2006 between Associates and the Issuer (incorporated herein by reference to Exhibits 10.30, 10.31 and 10.32 to the Issuer’s Current Annual Report on Form 10-K, filed on March 10, 2009).

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EX-99.A

EXHIBIT A

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1)(iii), we the undersigned agree that the Schedule 13D, to which this Joint Filing Agreement is attached as Exhibit A, is filed on behalf of each of us.

Dated:  December 1, 2009
HEARTLAND INDUSTRIAL ASSOCIATES L.L.C.
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member
HEARTLAND INDUSTRIAL PARTNERS, L.P.
By:  Heartland Industrial Associates L.L.C., its General Partner
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member
TRIMAS INVESTMENT FUND I, L.L.C.
By:  Heartland Industrial Associates L.L.C., the General Partner of Heartland Industrial Partners, L.P., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member
METALDYNE INVESTMENT FUND I, L.L.C.
By:  Heartland Industrial Associates L.L.C., the General Partner of Heartland Industrial Partners, L.P., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member

HIP SIDE-BY-SIDE PARTNERS, L.P.
By:  Heartland Industrial Associates L.L.C., its General Partner
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member
TRIMAS INVESTMENT FUND II, L.L.C.
By:  Heartland Industrial Associates L.L.C., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member
METALDYNE INVESTMENT FUND II, L.L.C.
By:  Heartland Industrial Associates L.L.C., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member
HIP SIDE-BY-SIDE I-A, L.L.C.
By:  Heartland Industrial Associates L.L.C., its Managing Member
By:	/s/ Daniel P. Tredwell
	Name:  Daniel P. Tredwell
	Title: Managing Member