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                                                                     EXHIBIT 4.3

                             SUPPLEMENTAL INDENTURE

                  SUPPLEMENTAL INDENTURE, dated as of May 10, 2002, among
Associated Materials Incorporated, a Delaware corporation (the "Company"), AMI
Management Company, a Delaware business trust ("AMC"), Wilmington Trust Company,
as trustee under the Indenture referred to below (the "Trustee"), and Alside,
Inc., a Delaware corporation ("Alside").

                              W I T N E S S E T H :

                  WHEREAS, the Company, AMC 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, Alside is a domestic Restricted Subsidiary of the
Company and has entered into the Supplement No. 1 to the Subsidiary Guaranty,
dated as of May 10, 2002, by and between Alside and UBS AG, Stamford Branch, as
administrative agent, to guarantee the Indebtedness under the Credit Agreement
as provided therein;

                  WHEREAS, this Supplemental Indenture has been duly authorized
by all necessary corporate action on the part of each of the Company, AMC and
Alside; 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, AMC, Alside and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders as follows:

                                    ARTICLE I

                                   Guaranties

                  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:

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                  "Subsidiary Guarantor" means AMI Management Company, 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. Alside 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. Alside. Alside agrees to be bound by the
Indenture and the Subsidiary Guaranties.

                  Section 1.4. Trustee's Acceptance. The Trustee hereby accepts
this 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 Supplemental Indenture. Upon the
execution and delivery of this Supplemental Indenture by the Company, AMC,
Alside 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 Supplemental Indenture Construed
Together. This Supplemental Indenture is an indenture supplemental to and in
implementation of the Indenture, the Indenture and this Supplemental Indenture
shall henceforth be read and construed together.

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

                  Section 2.5. Conflict with Trust Indenture Act. If any
provision of this 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 Supplemental Indenture, the provision of the TIA shall
control. If any provision of this 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 Supplemental Indenture, as the case may be.

                  Section 2.6. Severability. In case any provision in this
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.


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                  Section 2.7. Benefits of Supplemental Indenture. Nothing in
this 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 Supplemental
Indenture or the Securities.

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

                  Section 2.9. Certain Duties and Responsibilities of the
Trustee. In entering into this 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 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 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 Supplemental Indenture or for or in respect of the recitals contained
herein, all of which are made by the Company, AMC and Alside.


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                  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 and Chief
                                                Financial Officer


                                  AMI MANAGEMENT COMPANY



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


                                  ALSIDE, INC.

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

                                  WILMINGTON TRUST COMPANY,
                                        as Trustee

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


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