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	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
 Â	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* GGC Opportunity Fund Management GP, Ltd. (Last) (First) (Middle) C/O GOLDEN GATE PRIVATE EQUITY, INC. ONE EMBARCADERO CENTER 39TH FLOOR (Street) SAN FRANCISCO CA 94111 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Cornerstone Building Brands, Inc. [ CNR ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 02/19/2021
	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, $0.01 par value	02/19/2021		S		52,000	D	$11.58(1)	2,189,786	I	See note(2)(3)
Common Stock, $0.01 par value	02/22/2021		S		60,000	D	$11.64(4)	2,129,786	I	See note(2)(3)
Common Stock, $0.01 par value	02/23/2021		S		38,000	D	$11.54(5)	2,091,786	I	See note(2)(3)
Common Stock, $0.01 par value	02/24/2021		S		250,000	D	$11.87(6)	1,841,786	I	See note(2)(3)
Common Stock, $0.01 par value	02/25/2021		S		26,000	D	$11.6(7)	1,815,786	I	See note(2)(3)
Common Stock, $0.01 par value	02/26/2021		S		24,600	D	$11.52(8)	1,791,186	I	See note(2)(3)
Common Stock, $0.01 par value	03/01/2021		S		174,400	D	$11.78(9)	1,616,786	I	See note(2)(3)
Common Stock, $0.01 par value	03/02/2021		S		62,200	D	$11.53(10)	1,554,586	I	See note(2)(3)
Common Stock, $0.01 par value								12,441,252.41	I	See note(11)
Common Stock, $0.01 par value								48,150.31	I	See note(12)

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

1. Name and Address of Reporting Person* GGC Opportunity Fund Management GP, Ltd. (Last) (First) (Middle) C/O GOLDEN GATE PRIVATE EQUITY, INC. ONE EMBARCADERO CENTER 39TH FLOOR (Street) SAN FRANCISCO CA 94111 (City) (State) (Zip)

1. Name and Address of Reporting Person* GGCOF EXECUTIVE CO-INVEST, L.P. (Last) (First) (Middle) C/O GOLDEN GATE PRIVATE EQUITY, INC. ONE EMBARCADERO CENTER, 39TH FLOOR (Street) SAN FRANCISCO CA 94111 (City) (State) (Zip)

1. Name and Address of Reporting Person* GGCOF IRA CO-INVEST, L.P. (Last) (First) (Middle) C/O GOLDEN GATE PRIVATE EQUITY, INC. ONE EMBARCADERO CENTER, 39TH FLOOR (Street) SAN FRANCISCO CA 94111 (City) (State) (Zip)

Explanation of Responses:

1. Weighted average price representing high of $11.68 and low of $11.45.

2. Shares are directly held by AIC Finance Partnership, L.P. ("AIC"). Each of Golden Gate Capital Opportunity Fund, L.P. ("GGCOF"), Golden Gate Capital Opportunity Fund-A, L.P. ("GGCOF-A"), GGCOF Co-Invest, L.P. ("GGCOF Co-Invest"), GGCOF Co-Invest IRA, L.P. ("IRA Co-Invest") and GGCOF Executive Co-Invest, L.P. ("Executive Co-Invest" and, together with GGCOF, GGCOF-A, GGCOF Co-Invest and IRA Co-Invest, the "Funds") have an indirect pecuniary interest in AIC. GGCOF Co-Invest Management, L.P. ("GGCOF Third Party Co-Invest") is the general partner of each of GGCOF Co-Invest, IRA Co-Invest and Executive Co-Invest. GGC Opportunity Fund Management, L.P. ("Management GP") is the general partner of each of GGCOF, GGCOF-A and GGCOF Third Party Co-Invest, and GGC Opportunity Fund Management GP, Ltd.

3. (Continued from Footnote 3) ("Ultimate GP") is the general partner of Management GP. Ultimate GP is governed by its board of directors. Each of the Funds, GGCOF Third Party Co-Invest, Management GP and Ultimate GP disclaim beneficial ownership of these shares except to the extent of their respective pecuniary interests therein.

4. Weighted average price representing high of $11.83 and low of $11.50.

5. Weighted average price representing high of $11.60 and low of $11.50.

6. Weighted average price representing high of $12.10 and low of $11.57.

7. Weighted average price representing high of $12.01 and low of $11.50.

8. Weighted average price representing high of $11.69 and low of $11.50.

9. Weighted average price representing high of $12.01 and low of $11.67.

10. Weighted average price representing high of $11.81 and low of $11.50.

11. Shares are directly held by Atrium Intermediate Holdings, LLC ("Atrium Intermediate"). Atrium Window Holdings, LLC ("Atrium Holdings") and Atrium Window Parent, LLC ("Atrium Parent") are the members of Atrium Intermediate. Atrium Parent is the controlling unitholder of Atrium Holdings. GGC Atrium Window Holdings, LLC ("GGC Atrium') is the controlling unitholder of Atrium Parent. GGC BP Holdings, LLC ("GGC BP") is the controlling unitholder of GGC Atrium. The Funds collectively hold all of the equity interests of GGC BP. Each of Funds, GGCOF Third Party Co-Invest, Management GP and Ultimate GP disclaim beneficial ownership of these shares except to the extent of their respective pecuniary interests therein.

12. Shares are directly held by GGC BP. Each of the Funds, GGCOF Third Party Co-Invest, Management GP and Ultimate GP disclaim beneficial ownership of these shares except to the extent of their respective pecuniary interests therein.

Remarks:

Form 2 of 2

	GGC Opportunity Fund Management GP, Ltd., By: /s/ Stephen D. Oetgen, attorney-in-fact for David Dominik, a Director	03/02/2021
	GGC Atrium Window Holdings, LLC, By: /s/Stephen D. Oetgen, attorney-in-fact for David Thomas, a Manager	03/02/2021
	GGC BP Holdings, LLC, By: /s/ Stephen D. Oetgen, attorney-in-fact for David Thomas, a Manager	03/02/2021
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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