ECP Cardinal Holdings, LP - Dec 20, 2021 Form 3 Insider Report for Custom Truck One Source, Inc. (CTOS)

Role: Director, 10%+ Owner
Signature: ECP CARDINAL HOLDINGS, LP. By: NESCO Holdings GP, LLC, its general partner, By: /s/ Rahman D'Argenio, President
Stock symbol: CTOS
Transactions as of: Dec 20, 2021
Transactions value $: $0
Form type: 3
Date filed: 12/29/2021, 03:15 PM

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
holding	CTOS	Common Stock						25.9M	Dec 20, 2021	See Footnotes	F1, F2, F3

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Includes: 4,500,000 shares held of record by ECP Cardinal Holdings, LP, which were formerly held directly by Energy Capital Partners III, LP, Energy Capital Partners III-A, LP, Energy Capital Partners III-B, LP, Energy Capital Partners III-C, LP, and Energy Capital Partners III-D, LP. and contributed to ECP Cardinal Holdings, LP. Also includes 21,238,988 shares held of record by NESCO Holdings, LP and 107,148 shares of Common Stock and 13,631 restricted stock units beneficially owned by Energy Capital Partners Management, L.P.
F2	The general partner of each of ECP Cardinal Holdings, LP and NESCO Holdings, LP is NESCO Holdings GP, LLC. Energy Capital Partners III, LP, Energy Capital Partners III-A, LP, Energy Capital Partners III-B, LP, Energy Capital Partners III-C, LP, and Energy Capital Partners III-D, LP (together, the "ECP III Funds") and Energy Capital Partners III (NESCO Co-Invest), LP are the sole members of NESCO Holdings GP, LLC. Energy Capital Partners III, LLC is the general partner of (i) Energy Capital Partners GP III, LP, which is the general partner of each of the ECP III Funds, and (ii) Energy Capital Partners GP III Co-Investment (NESCO), LLC, which is the general partner of Energy Capital Partners III (NESCO Co-Invest), LP. As a result, each of the foregoing entities may be deemed to share beneficial ownership of the shares of Common Stock held by ECP Cardinal Holdings, LP and Nesco Holdings LP.
F3	(Continued) ECP Management GP, LLC is the general partner of Energy Capital Partners Management, LP and may be deemed to share beneficial ownership of the securities beneficially owned by Energy Capital Partners Management, LP. ECP ControlCo, LLC is the sole member of Energy Capital Partners III, LLC and the sole member of ECP Management GP, LLC and may be deemed to share beneficial ownership of the securities beneficially owned be each of Energy Capital Partners III, LLC and ECP Management GP, LLC. The managing members of ECP ControlCo, LLC are Douglas Kimmelman, Andrew Singer, Peter Labbat, Tyler Reeder and Rahman D'Argenio all of whom collectively share the power to vote and dispose of the securities beneficially owned by ECP ControlCo, LLC. Each of the foregoing individuals and entities disclaims beneficial ownership of the securities reported herein except to the extent of his or its pecuniary interest therein.