Exhibit 4.3



 Exhibit 4.3 

Execution Version 
 SECOND
SUPPLEMENTAL INDENTURE 
 Second Supplemental Indenture (this “Supplemental Indenture”), dated as of December 1, 2015,
among each subsidiary of the Successor Issuer (as defined below) that is a signatory hereto (each, a “Guaranteeing Subsidiary” and, collectively, the “Guaranteeing Subsidiaries”), upon consummation of the Merger (as
defined below), the Successor Issuer (as successor in interest to the Issuer referred to and as defined below), a Delaware corporation, and Wilmington Trust, National Association, as trustee (under the Indenture referred to below) (the
“Trustee”). 
 W I T N E S S E T H 

WHEREAS, Building Materials Holdings Corporation, a Delaware corporation (the “Issuer”), has heretofore executed and
delivered to the Trustee an indenture (as amended, supplemented or otherwise modified prior to the date hereof, including pursuant to the First Supplemental Indenture, dated as of June 1, 2015 among VNS Corporation, ProCon Construction
Services, LLC, and TrussMart Building Components, LLC, and the Trustee, the “Indenture”), dated as of September 20, 2013, providing for the issuance of an unlimited aggregate principal amount of 9.0% Senior Secured Notes due
2018 (the “Notes”); 
 WHEREAS, the Indenture provides that the Issuer will not merge into another Person unless the
successor Person assumes by supplemental indenture all of the Issuer’s Obligations under the Notes; 
 WHEREAS, on the date hereof, the
Issuer is merging with and into Stock Building Supply Holdings, Inc. (the “Merger”), which, upon consummation of the Merger, shall change its legal entity name to BMC Stock Holdings, Inc. (the “Successor Issuer”),
at the “Effective Time” specified in the certificate of merger relating thereto to be filed concurrently herewith with the Secretary of State of Delaware (the “Effective Time”); 

WHEREAS, pursuant to Section 9.01(3) and 9.01(4) of the Indenture, the Successor Issuer and the Trustee are authorized to execute and
deliver this Supplemental Indenture to amend or supplement the Indenture without the consent of any Holder; 
 WHEREAS, the Indenture
provides that under certain circumstances the Guaranteeing Subsidiaries shall execute and deliver to the Trustee a supplemental indenture pursuant to which the Guaranteeing Subsidiaries shall unconditionally guarantee all of the Issuer’s
Obligations under the Notes and the Indenture on the terms and conditions set forth herein and under the Indenture (the “Guarantee”); and 

WHEREAS, pursuant to Section 9.01(9) of the Indenture, the Trustee, the Successor Issuer and Guaranteeing Subsidiaries are authorized to
execute and deliver this Supplemental Indenture without the consent of any Holder. 







 NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration,
the receipt of which is hereby acknowledged, the parties mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows: 

(1) Capitalized Terms. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture. 

(2) Assumption of Obligations. As of the Effective Time and after giving effect to the Merger, the Successor Issuer hereby expressly
assumes all of the Issuer’s Obligations under the Notes and the Indenture. 
 (3) Agreement to Guarantee. Each Guaranteeing
Subsidiary hereby agrees to be a Guarantor under the Indenture and to be bound by the terms of the Indenture applicable to Guarantors, including Article 10 thereof. 

(4) Execution and Delivery. Each Guaranteeing Subsidiary agrees that the Guarantee shall remain in full force and effect notwithstanding
the absence of the endorsement of any notation of such Guarantee on the Notes. 
 (5) Governing Law. THIS SUPPLEMENTAL INDENTURE WILL
BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK. 
 (6) Counterparts. The parties may sign any
number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement. 

(7) Effect of Headings. The Section headings herein are for convenience only and shall not affect the construction hereof. 

(8) The Trustee. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this
Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Successor Issuer and the Guaranteeing Subsidiaries. 

[Signature page follows] 

  
 2 








 IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly
executed, all as of the date first above written. 
  

					
	 BUILDING MATERIALS HOLDINGS

CORPORATION, a Delaware corporation, and upon consummation of the Merger with STOCK 

BUILDING SUPPLY HOLDINGS, INC., BMC
 STOCK HOLDINGS,
INC.
  
 By: /s/ Peter Alexander

Name: Peter Alexander
 Title: Chief Executive Officer
	  		  	
	  
 COLEMAN FLOOR, LLC, a

Delaware limited liability company
  

By: /s/ James F. Major, Jr. 
 Name: James F. Major,
Jr.
 Title: Executive Vice President and Chief Financial

Officer
	  		  	  
 STOCK BUILDING SUPPLY, LLC, a North

Carolina limited liability company
  

By: /s/ James F. Major, Jr. 
 Name: James F. Major,
Jr.
 Title: Executive Vice President and Chief Financial

Officer

		  		  	  
 STOCK BUILDING SUPPLY MIDWEST,

LLC, a Delaware limited liability company
  

By: /s/ James F. Major, Jr. 
 Name: James F. Major,
Jr.
 Title: Executive Vice President and Chief Financial

Officer

	  
 STOCK BUILDING SUPPLY WEST, LLC, a

Utah limited liability company
  

By: /s/ James F. Major, Jr. 
 Name: James F. Major,
Jr.
 Title: Executive Vice President and Chief Financial

Officer
	  		  	  
 STOCK BUILDING SUPPLY OF ARKANSAS,

LLC, a Delaware limited liability company
  

By: /s/ James F. Major, Jr. 
 Name: James F. Major,
Jr.
 Title: Executive Vice President and Chief Financial

Officer



  
 Signature Page to
Second Supplemental Indenture 









					
	 SBS / BISON BUILDING MATERIALS, LLC,
 a
Delaware limited liability company
  
 By: /s/ James F. Major, Jr. 

Name: James F. Major, Jr.
 Title: Executive Vice President and
Chief Financial Officer
	 		  	 COLEMAN FLOOR SOUTHEAST, LLC, a
 Delaware
limited liability company
  
 By: /s/ James F. Major, Jr. 

Name: James F. Major, Jr.
 Title: Executive Vice President and
Chief Financial
 Officer

	  
 TBSG, LLC, a Delaware limited liability company

 
 By: /s/ James F. Major, Jr. 

Name: James F. Major, Jr.
 Title: Executive Vice President and
Chief Financial
 Officer
	 		  	  
 SBS GUILFORD, LLC, a Delaware limited liability company

 
 By: /s/ James F. Major, Jr. 

Name: James F. Major, Jr.
 Title: Executive Vice President and
Chief Financial Officer

	  
 STOCK WINDOW AND DOOR SOUTHEAST,

LLC, a Delaware limited liability company
  

By: /s/ James F. Major, Jr. 
 Name: James F. Major,
Jr.
 Title: Executive Vice President and Chief Financial

Officer
	 		  	  
 STOCK BUILDING SUPPLY WEST (USA),

INC., a Delaware corporation
  

By: /s/ James F. Major, Jr. 
 Name: James F. Major,
Jr.
 Title: Executive Vice President and Chief Financial Officer



  
 Signature Page to
Second Supplemental Indenture 








 
			
	WILMINGTON TRUST, NATIONAL ASSOCIATION, as Trustee
		
	By:	 	 /s/ Jane Schweiger

		 	Name: Jane Schweiger
		 	Title: Vice President



  
 Signature Page to
Second Supplemental Indenture