Exhibit 4.6  FIRST SUPPLEMENTAL INDENTURE   FIRST
SUPPLEMENTAL INDENTURE, dated as of December 29, 2005 between HBP
Acquisition LLC, a Delaware limited liability company (the New Guarantor),
the Company, the Existing Guarantors and Wilmington Trust Company, as trustee
under the Indenture referred to below (the Trustee).  W I T N E S S E T H :  WHEREAS,
Building Materials Corporation of America, a Delaware corporation (the Company),
certain guarantors named therein and the Trustee heretofore executed and
delivered the Indenture, dated as of July 26, 2004 (as heretofore amended
and supplemented, the Indenture), providing for the issuance of the 7.75%
Senior Notes Due 2014 and the Series B 7.75% Senior Notes Due 2014
(collectively, the Securities) (capitalized terms used herein but not
otherwise defined have the meanings ascribed thereto in the Indenture);  WHEREAS,
as a result of the guarantee by the New Guarantor of the Credit Agreement,
pursuant to Section 4.18 of the Indenture the Company is required to cause
the New Guarantor to execute and deliver to the Trustee this First Supplemental
Indenture pursuant to which the New Guarantor shall provide a Guarantee as set
forth in Article X of the Indenture;  WHEREAS,
Section 9.01(5) of the Indenture provides that the Company, the
Guarantors and the Trustee may amend the Indenture and the Securities without
notice to or consent of any Holders of the Securities to add Subsidiary
Guarantees; and  WHEREAS,
this First Supplemental Indenture has been duly authorized by all necessary
corporate action on the part of the New Guarantor.  NOW,
THEREFORE, in consideration of the premises and for other good and valuable
consideration, the receipt of which is hereby acknowledged, the Company, the
existing Guarantors, the New Guarantor and the Trustee mutually covenant and
agree for the equal and ratable benefit of the Holders as follows:  ARTICLE I  Agreement to Guarantee  Section 1.1.  Agreement to Guarantee.  Subject to Section 10.07 of the
Indenture, the New Guarantor hereby agrees, jointly and severally with all
other Guarantors, irrevocably and unconditionally, to guarantee the punctual
payment when due, whether at maturity, by acceleration, by redemption or
otherwise, of all other monetary obligations of the Company under the indenture
and the Securities on the terms and subject to the conditions set forth in Article X
of the Indenture, which guarantee shall


be
subject to automatic release in accordance with the provisions of Section 10.09
of the Indenture.  Section 1.2.  Trustees Acceptance.  The Trustee hereby accepts this First
Supplemental Indenture and agrees to perform the same under terms and
conditions set forth in the Indenture.  ARTICLE II  Miscellaneous  Section 2.1.  Effect of First Supplemental Indenture.  Upon the execution and delivery of this First
Supplemental Indenture by the Company, the existing Guarantors, the New
Guarantor and the Trustee, the Indenture shall be supplemented in accordance
herewith, and this First Supplemental Indenture shall form a part of the
Indenture for all purposes, and every Holder of Securities heretofore or
hereafter authenticated and delivered under the Indenture shall be bound
thereby.  Section 2.2.  Indenture Remains in Full Force and Effect.  Except as supplemented hereby, all provisions
in the Indenture shall remain in full force and effect.  Section 2.3.  Indenture and First Supplemental Indenture
Construed Together.  This First
Supplemental Indenture is an indenture supplemental to and implementation of
the Indenture, and the Indenture and this First Supplemental Indenture shall
henceforth be read and construed together.  Section 2.4.  Confirmation and Preservation of Indenture.  The Indenture as supplemented by this First
Supplemental Indenture is in all respects confirmed and preserved.  Section 2.5.  Conflict with Trust Indenture Act.  If any provision of this First Supplemental
Indenture limits, qualifies or conflicts with any provision of the TIA that is
required under the TIA to be part of and govern any provision of this First
Supplemental Indenture, the provision of the TIA shall control.  If any provision of this First Supplemental
Indenture modifies or excludes any provision of the TIA that may be so modified
or excluded, the provision of the TIA shall be deemed to apply to the Indenture
as so modified or to be excluded by this First Supplemental Indenture, as the
case may be.  Section 2.6.  Severability.  In case any provision in this First
Supplemental Indenture shall be invalid, illegal or unenforceable, the
validity, legality and enforceability of the remaining provisions shall not in
any way be affected or impaired thereby.  Section 2.7.  Benefits of First Supplemental Indenture.  Nothing in this First Supplemental Indenture
or the Securities, express or implied, shall give to any   2


Person,
other than the parties hereto and thereto and their successors hereunder and
thereunder and the Holders of the Securities, any benefit of any legal or
equitable right, remedy or claim under the Indenture, this First Supplemental
Indenture or the Securities.  Section 2.8.  Successors.  All agreements of the New Guarantor in this
First Supplemental Indenture shall bind its successors except as provided in
the Indenture.  All agreements of the
Trustee in this First Supplemental Indenture shall bind its successors.  Section 2.9.  Certain Duties and Responsibilities of the
Trustee.  In entering into this First
Supplemental Indenture, the Trustee shall be entitled to the benefit of every
provision of the Indenture and the Securities relating to the conduct or
affecting the liability or affording protection to the Trustee, whether or not
elsewhere herein so provided.  Section 2.10.  Governing Law.  This First Supplemental Indenture shall be
governed by, and construed in accordance with, the laws of the State of New
York. The Trustee, the Company, the Guarantors and the Securityholders agree to
submit to the jurisdiction of the courts of the State of New York in any action
or proceeding arising out of or relating to this Indenture or the Securities.  Section 2.11.  Multiple Originals.  The parties may sign any number of copies of
this First Supplemental Indenture.  Each
signed copy shall be an original, but all of them together represent the same
agreement.  One signed copy is enough to
prove this First Supplemental Indenture.  Section 2.12.  Headings.  The Article and Section headings
herein are have been inserted for convenience of reference only, are not
intended to be considered a part hereof and shall not modify or restrict any of
the terms or provisions hereof.   3


IN
WITNESS WHEREOF, the parties hereto have caused this First Supplemental
Indenture to be duly executed as of the date first written above.  New GuarantorHBP
  ACQUISITION LLCBy:
  /s/
  John M. MaitnerName:
  John
  M. MaitnerTitle:
  Vice
  President and TreasurerCompanyBUILDING
  MATERIALSCORPORATION
  OF AMERICABy:
  /s/
  John M. MaitnerName:
  John
  M. MaitnerTitle:
  Vice
  President and Treasurer


Existing GuarantorsBMCA INSULATION PRODUCTS
  INC.BMCA QUAKERTOWN INC.BUILDING MATERIALS
  INVESTMENT CORPORATIONBUILDING MATERIALS
  MANUFACTURING CORPORATIONDUCTWORK MANUFACTURING
  CORPORATIONGAF LEATHERBACK CORP.GAF MATERIALS CORPORATION
  (CANADA)GAF PREMIUM PRODUCTS INC.GAF REAL PROPERTIES, INC.GAFTECH CORPORATIONLL BUILDING PRODUCTS INC.PEQUANNOCK VALLEY CLAIM
  SERVICE COMPANY, INC.SOUTH PONCA REALTY CORP.WIND GAP REAL PROPERTY
  ACQUISITION CORP.,By:
  /s/
  John M. MaitnerName:
  John
  M. MaitnerTitle:
  Vice
  President and Treasurer


TrusteeWILMINGTON
  TRUST COMPANYBy:
  /s/
  Kristin L. MooreName:
  Kristin
  L. MooreTitle:
  Financial
  Services Officer