Custom Truck One Source (CTOS) Form 4 Change in insider ownership

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

ECP ControlCo, LLC

(Last) (First) (Middle)

40 BEECHWOOD ROAD,

(Street)

SUMMIT, NJ 07901

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Custom Truck One Source, Inc. [ CTOS ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
03/31/2024

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/31/2024		M		18,640	A	$0(1)	18,640	I	See footnote(2)
Common Stock								25,738,988	I	See footnotes(3)(4)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Unit	(1)	03/31/2024		M			18,640	(5)	(5)	Common Stock	18,640	$0	0	I	See footnote(2)
Restricted Stock Unit	(1)	04/01/2024		A		22,218		(6)	(6)	Common Stock	22,218	$0	22,218	I	See footnote(2)

1. Name and Address of Reporting Person^*

ECP ControlCo, LLC

(Last) (First) (Middle)

40 BEECHWOOD ROAD,

(Street)

SUMMIT, NJ 07901

(City) (State) (Zip)

1. Name and Address of Reporting Person^*

ECP Management GP, LLC

(Last) (First) (Middle)

40 BEECHWOOD ROAD,

(Street)

SUMMIT, NJ 07901

(City) (State) (Zip)

1. Name and Address of Reporting Person^*

Energy Capital Partners Management, LP

(Last) (First) (Middle)

40 BEECHWOOD ROAD,

(Street)

SUMMIT, NJ 07901

(City) (State) (Zip)

Explanation of Responses:

1. Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock.

2. Represents securities held directly by Energy Capital Partners Management, LP ("ECP Management"). ECP Management GP, LLC is the general partner of ECP Management and may be deemed to share beneficial ownership of the securities held by ECP Management. ECP ControlCo, LLC ("ECP ControlCo") is the sole member of ECP Management GP, LLC. As a result, ECP ControlCo may be deemed to share beneficial ownership of the securities beneficially owned by ECP Management GP, LLC. The managing members of ECP ControlCo 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. Each such individual disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein.

3. Includes 21,238,988 shares held by NESCO Holdings, LP and 4,500,000 shares held by ECP Cardinal Holdings, LP ("ECP Cardinal"). The general partner of each of ECP Cardinal and NESCO Holdings, LP is NESCO Holdings GP, LLC. ECP Starlight Guarantor (Public), LP ("ECP Starlight") and Energy Capital Partners III (NESCO Co-Invest), LP are the sole members of NESCO Holdings GP, LLC.

4. ECP ControlCo is the sole member of Energy Capital Partners III, LLC, which is the general partner of (i) Energy Capital Partners GP III, LP, which is the general partner of each of 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"), which are the sole members of ECP Starlight Public GP, LLC, which is the general partner of ECP Starlight, 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 and NESCO Holdings, LP.

5. The restricted stock units vested in full on March 31, 2024.

6. The restricted stock units will vest on March 31, 2025 and have no expiration date.

	ECP ControlCo, LLC By: /s/ Rahman D'Argenio, Managing Member	04/02/2024
	ECP Management GP, LLC By: ECP ControlCo, LLC, its sole member By: /s/ Rahman D'Argenio, Managing Member	04/02/2024
	ECP ControlCo, LLC By: ECP Management GP, LLC, its general partner By: ECP ControlCo, LLC, its sole member By: /s/ Rahman D'Argenio, Managing Member	04/02/2024
	** Signature of Reporting Person	Date
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