<PAGE>
                                                                    EXHIBIT 4.6

                          SECOND SUPPLEMENTAL INDENTURE

                  SECOND SUPPLEMENTAL INDENTURE, dated as of August 29, 2003,
among Associated Materials Incorporated, a Delaware corporation (the "Company"),
Alside, Inc., a Delaware corporation ("Alside"), Wilmington Trust Company, as
trustee under the Indenture referred to below (the "Trustee"), and each of the
other Guarantors listed on Schedule A attached hereto ("Guarantors").

                                  WITNESSETH:

                  WHEREAS, the Company, AMI Management Company and the Trustee
heretofore executed and delivered an Indenture, dated as of April 23, 2002 (as
heretofore amended and supplemented, the "Indenture"), providing for the
issuance of the 9 3/4% Senior Subordinated Notes due 2012 (the "Securities")
(capitalized terms used herein but not otherwise defined have the meanings
ascribed thereto in the Indenture);

                  WHEREAS, Section 4.10 of the Indenture provides that each
domestic Restricted Subsidiary of the Company that guarantees or incurs any
Indebtedness under the Credit Agreement shall execute and deliver to the Trustee
a Guaranty Agreement, pursuant to which such Restricted Subsidiary shall
Guarantee payment of the Securities on the same terms and conditions as those
set forth in the Indenture;

                  WHEREAS, Section 9.01 of the Indenture provides that the
Company may amend the Indenture without notice to or consent of any
Securityholder to add guarantees with respect to the Securities, including any
Subsidiary Guaranties, or to secure the Securities;

                  WHEREAS, each of the Guarantors is a domestic Restricted
Subsidiary of the Company and has entered into agreements to guarantee the
Indebtedness under the Credit Agreement as provided therein;

                  WHEREAS, this Second Supplemental Indenture has been duly
authorized by all necessary corporate action on the part of each of the Company,
Alside and the Guarantors; and

                  WHEREAS, all conditions precedent to supplement the Indenture
have been met;

                  NOW, THEREFORE, in consideration of the premises and for other
good and valuable consideration, the receipt of which is hereby acknowledged,
the Company, Alside, the Guarantors and the Trustee mutually covenant and agree
for the equal and ratable benefit of the Holders as follows:


                                    ARTICLE I

                                   Guaranties

<PAGE>

                  Section 1.1. Subsidiary Guarantor. The definition of
"Subsidiary Guarantor" set forth in Section 1.01 of the Indenture is hereby
amended to read in its entirety as follows:

                  "Subsidiary Guarantor" means Alside, Inc. and each domestic
Subsidiary of the Company that executes this Indenture as a guarantor on the
Issue Date and each other domestic Subsidiary of the Company that thereafter
guarantees the Securities pursuant to the terms of this Indenture."

                  Section 1.2. Subsidiary Guaranty. Each of the Guarantors
hereby agrees, jointly and severally with all other Subsidiary Guarantors, to
guarantee the Company's Obligations under the Securities and the Indenture on
the terms and subject to the conditions set forth in Articles 11 and 12 of the
Indenture and to be bound by all other applicable provisions of the Indenture.

                  Section 1.3. Trustee's Acceptance. The Trustee hereby accepts
this Second Supplemental Indenture and agrees to perform the same under the
terms and conditions set forth in the Indenture.

                                   ARTICLE II

                                  Miscellaneous

                  Section 2.1. Effect of Second Supplemental Indenture. Upon the
execution and delivery of this Second Supplemental Indenture by the Company,
Alside, each of the Guarantors and the Trustee, the Indenture shall be
supplemented in accordance herewith, and this 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 Second Supplemental Indenture
Construed Together. This Second Supplemental Indenture is an indenture
supplemental to and in implementation of the Indenture. The Indenture and this
Second Supplemental Indenture shall henceforth be read and construed together.

                  Section 2.4. Confirmation and Preservation of Indenture. The
Indenture as supplemented by this Second Supplemental Indenture is in all
respects confirmed and preserved.

                  Section 2.5. Conflict with Trust Indenture Act. If any
provision of this Second 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 Second Supplemental

Indenture, the provision of the TIA shall control. If any provision of this
Second 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 Second
Supplemental Indenture, as the case may be.

                  Section 2.6. Severability. In case any provision in this
Second Supplemental Indenture shall be invalid, illegal or unenforceable, the

<PAGE>

validity, legality and enforceability of the remaining provisions shall not in
any way be affected or impaired thereby.

                  Section 2.7. Benefits of Supplemental Indenture. Nothing in
this Second Supplemental Indenture or the Securities, express or implied, shall
give to any 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 Second Supplemental Indenture or the Securities.

                  Section 2.8. Successors. All agreements of the Company, Alside
and the Guarantors in this Second Supplemental Indenture shall bind its
successors. All agreements of the Trustee in this Second Supplemental Indenture
shall bind its successors.

                  Section 2.9. Certain Duties and Responsibilities of the
Trustee. In entering into this Second 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 Second Supplemental
Indenture shall be governed by, and construed in accordance with, the laws of
the State of New York but without giving effect to applicable principles of
conflicts of law to the extent that the application of the laws of another
jurisdiction would be required thereby.

                  Section 2.11. Multiple Originals. The parties may sign any
number of copies of this Second Supplemental Indenture, each of which shall be
deemed an original, but all of which together shall constitute one and the same
instrument.

                  Section 2.12. Headings. The Article and Section headings
herein are 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.

                  Section 2.13. The Trustee. The Trustee shall not be
responsible in any manner for or in respect of the validity or sufficiency of
this Second Supplemental Indenture or for or in respect of the recitals
contained herein, all of which are made by the Company, Alside and the
Guarantors.

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

                        ASSOCIATED MATERIALS INCORPORATED

                        By: /s/ D. Keith LaVanway
                            --------------------------------------------------
                            Name: D. Keith LaVanway
                            Title: Vice President-Chief Financial Officer,
                                   Treasurer and Secretary

                        ALSIDE, INC.

                        By: /s/ D. Keith LaVanway
                            --------------------------------------------------
                            Name: D. Keith LaVanway

<PAGE>


                            Title: Vice President, Treasurer and Secretary

                        GENTEK HOLDINGS, INC.

                        By: /s/ D. Keith LaVanway
                            --------------------------------------------------
                            Name: D. Keith LaVanway
                            Title: Vice President-Chief Financial Officer,
                                   Treasurer and Secretary


                        GENTEK BUILDING PRODUCTS, INC.

                        By: /s/ D. Keith LaVanway
                            --------------------------------------------------
                            Name: D. Keith LaVanway
                            Title: Vice President-Chief Financial Officer,
                                  Treasurer and Secretary


                        WILMINGTON TRUST COMPANY,
                                   as Trustee

                        By: /s/ Michael G. Oller, Jr.
                            ------------------------------------------------
                            Name: Michael G. Oller, Jr.
                            Title: Senior Financial Services Officer

<PAGE>


                                                                      Schedule A

                                   Guarantors

Gentek Holdings, Inc.

Gentek Building Products, Inc.