Exhibit 4.11  SIXTH SUPPLEMENTAL INDENTURE  SIXTH
SUPPLEMENTAL INDENTURE, dated as of March 26, 2007 between the companies
listed on Schedule A hereto (collectively, the New Guarantors),
Building Materials Corporation of America, a Delaware corporation (the Company),
the existing Guarantors signatory hereto (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,
Indenture dated as of July 26, 2004 (as heretofore amended and
supplemented, the Indenture), was executed and delivered by the
Company, certain guarantors named therein and the Trustee, 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 guarantees by the New Guarantors of the Credit Agreement,
pursuant to Section 4.18 of the Indenture, the Company is required to
cause the New Guarantors to execute and deliver to the Trustee this Sixth
Supplemental Indenture pursuant to which the New Guarantors shall provide
Guarantees 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 Sixth Supplemental Indenture has been duly authorized by all necessary
corporate, limited liability company or similar action on the part of the New
Guarantors.  NOW,
THEREFORE, in consideration of the premises set forth above and for other good
and valuable consideration, the receipt of which is hereby acknowledged, the
Company, the Existing Guarantors, the New Guarantors 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 Guarantors hereby agree, 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 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 guarantees 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 Sixth
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 Sixth Supplemental Indenture.  Upon the execution and delivery of this Sixth
Supplemental Indenture by the Company, the Existing Guarantors, the New
Guarantors and the Trustee, the Indenture shall be supplemented in accordance
herewith, and this Sixth 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 Sixth Supplemental Indenture
Construed Together.  This Sixth
Supplemental Indenture is an indenture supplemental to in and implementation of
the Indenture, and the Indenture and this Sixth Supplemental Indenture shall
henceforth be read and construed together.  Section 2.4.  Confirmation and Preservation of Indenture.  The Indenture as supplemented by this Sixth
Supplemental Indenture is in all respects confirmed and preserved.  Section 2.5.  Conflict with Trust Indenture Act.  If any provision of this Sixth 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 Sixth
Supplemental Indenture, the provision of the TIA shall control.  If any provision of this Sixth 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 Sixth Supplemental Indenture, as the
case may be.  Section 2.6.  Severability.  In case any provision in this Sixth
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 Sixth Supplemental Indenture.  Nothing in this Sixth 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 Sixth Supplemental
Indenture or the Securities.  Section 2.8.  Successors.  All agreements of the New Guarantor in this
Sixth Supplemental Indenture shall bind its successors except as provided in
the Indenture.  All agreements of the
Trustee in this Sixth Supplemental Indenture shall bind its successors.  Section 2.9.  Certain Duties and Responsibilities of the
Trustee.  In entering into this Sixth
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 Sixth 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 the Indenture, this Sixth
Supplemental Indenture or the Securities.  Section 2.11.  Multiple Originals.  The parties may sign any number of copies of
this Sixth 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 Sixth Supplemental Indenture.  Section 2.12.  Headings.  The Article and Section headings
herein 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 Sixth Supplemental
Indenture to be duly executed as of the date first written above.  New GuarantorsELKCORPELK PREMIUM BUILDING PRODUCTS,
  INC.ELK
  CORPORATION OF AMERICAELK
  CORPORATION OF ALABAMAELK
  CORPORATION OF TEXASELK
  CORPORATION OF ARKANSASELK PERFORMANCE NONWOVEN 
  FABRICS,INC.ELK COMPOSITE BUILDING PRODUCTS, 
  INC.RGM
  PRODUCTS, INC.RIDGEMATE
  MANUFACTURING CO. INC.ELK
  SLATE PRODUCTS, INC.ELK VERSASHIELD BUILDING 
  SOLUTIONS, INC.ELK TECHNOLOGY GROUP, INC.CHROMIUM
  CORPORATIONELK
  TECHNOLOGIES, INC.MIDLAND
  PATH FORWARD, INC.LUFKIN
  PATH FORWARD, INC.ELK
  GROUP, INC.ELK
  GROUP, L.P.NELPA,
  INC.By:
  /s/CompanyBUILDING MATERIALS CORPORATION
  OF AMERICABy:
  /s/ John MaitnerName:    John MaitnerTitle:      Vice
  President, Treasurer


Existing GuarantorsBUILDING MATERIALS
  INVESTMENTCORPORATIONBMCA ACQUISITION INC.BMCA ACQUISITION SUB. INC.BMCA FRESNO LLCBMCA FRESNO II LLCBMCA GAINESVILLE LLCBMCA INSULATION PRODUCTS
  INC.BUILDING MATERIALSMANUFACTURING CORPORATIONDUCTWORK MANUFACTURING
  CORPORATIONGAF LEATHERBACK CORP.GAF MATERIALS CORPORATION
  (CANADA)GAF PREMIUM PRODUCTS INC.GAF REAL PROPERTIES, INC.GAFTECH CORPORATIONLL BUILDING PRODUCTS INC.PEQUANNOCK VALLEY CLAIMSERVICE COMPANY, INC.SOUTH PONCA REALTY CORP.BMCA QUAKERTOWN INC.WIND GAP REAL PROPERTY
  ACQUISITION CORP.HBP ACQUISITION LLCBy:
  /s/ John MaitnerName:    John
  MaitnerTitle:      Vice
  President, Treasurer


TrusteeWILMINGTON
  TRUST COMPANYBy:
  /s/ Kristin L. MooreName:   Kristin
  L. MooreTitle:     Authorized
  Signatory


Schedule A  New
  Guarantors:ElkcorpElk
  Premium Building Products, Inc.Elk
  Corporation Of AmericaElk
  Corporation Of AlabamaElk
  Corporation Of TexasElk
  Corporation Of ArkansasElk
  Performance Nonwoven Fabrics, Inc.Elk
  Composite Building Products, Inc.RGM
  Products, Inc.Ridgemate
  Manufacturing Co. Inc.Elk
  Slate Products, Inc.Elk
  VersaShield Building Solutions, Inc.Elk
  Technology Group, Inc.Chromium
  CorporationElk
  Technologies, Inc.Midland
  Path Forward, Inc.Lufkin
  Path Forward, Inc.Elk
  Group, Inc.Elk
  Group, L.P.NELPA, Inc.