Commitments and contingencies

(a) Operating lease commitments

The Company rents equipment, office, and warehouse space at various locations in the United States and Canada under noncancelable operating leases. Rental expense was $24,900, $20,296, and $19,203 for the years ended December 31, 2018, 2017 and 2016, respectively. Approximate annual future commitments under noncancelable operating leases as of December 31, 2018 are as follows:



	Amount
2019	$	15,911
2020	15,219
2021	13,454
2022	12,561
2023	11,133
Thereafter	45,324
Total	$	113,602

(b) Legal matters

From time to time, and in the ordinary course of business, the Company is subject to various claims, charges, and litigation, such as employment-related claims and slip and fall cases. The Company is not currently aware of any legal proceedings or claims that the Company believes will have, individually or in the aggregate, a material adverse effect on the Company’s financial position or result of operations.

As of December 31, 2018, the Company had advertising purchase commitments of approximately $17,848, including commitments made by the NAF. In addition, the Company had open purchase orders of approximately $18,189 primarily related to equipment to be sold to franchisees.

(d) Guarantees

The Company has guaranteed certain leases of entities that were previously related through common ownership. These guarantees relate to leases for operating space of franchises operated by the related entities. The Company’s maximum obligation, as a result of its guarantees of leases, is approximately $732 and $979 as of December 31, 2018 and 2017, respectively, and would only require payment upon default by the primary obligor. The Company has determined the fair value of these guarantees at inception is not material, and as of December 31, 2018 and 2017, no accrual has been recorded for the Company’s potential obligation under its guaranty arrangement.