<PAGE>

                                                                [EXECUTION COPY]

                                JOINDER AGREEMENT

      This JOINDER AGREEMENT (this "Joinder"), dated as of August 31, 1999, by
B.W. ELLIOTT MANUFACTURING CO., LLC, a limited liability company organized under
the laws of the State of New York, HUDSON LOCK, LLC, a limited liability company
organized under the laws of the State of Delaware, ESP LOCK PRODUCTS, LLC, a
limited liability company organized under the laws of the State of Delaware,
GITS MANUFACTURING COMPANY, LLC, a limited liability company organized under the
laws of the State of Delaware, MARINE INDUSTRIES COMPANY, LLC, a limited
liability company organized under the laws of the State of Delaware, and TURNER
ELECTRIC, LLC, a limited liability company organized under the laws of the State
of Delaware (each a "Joining Party" and, collectively, the "Joining Parties"),
is delivered to SOCIETE GENERALE, as Agent (the "Agent") for the Lenders
referred to below, pursuant to the Credit Agreement, dated as of January 19,
1999 (as amended, supplemented or otherwise modified from time to time, the
"Credit Agreement"), among KEY COMPONENTS, LLC, as Borrower, each of the
Subsidiaries of the Borrower identified as Guarantors in the Credit Agreement
(the "Guarantors"), the various financial institutions from time to time party
thereto (the "Lenders") and the Agent. Terms used herein but not defined herein
shall have the meanings provided for in the Credit Agreement unless otherwise
specified.

      Each Joining Party has been created by the Borrower, and as such each
Joining Party is required, pursuant to Section 7.1.8 of the Credit Agreement, to
become a Guarantor and an Obligor under the Credit Agreement and, accordingly,
agrees as follows:

            1. By this Joinder, such Joining Party becomes a Guarantor and an
      Obligor under the Credit Agreement for all purposes under the Credit
      Agreement.

            2. By this Joinder, such Joining Party becomes a Grantor (as such
      term is defined in the Security Agreement defined below) under the Amended
      and Restated Guarantor Security Agreement, dated as of January 19, 1999
      (the "Security Agreement"), for all purposes under the Security Agreement.
<PAGE>

      IN WITNESS WHEREOF, each Joining Party has caused this Joinder to be duly
executed as of the date first above written.

                                        JOINING PARTIES

                                        B.W. ELLIOTT MANUFACTURING CO., LLC

                                        By: /s/ Alan L. Rivera
                                           -------------------------------------
                                           Name:  Alan L. Rivera
                                           Title: Assistant Secretary


                                        HUDSON LOCK, LLC

                                        By: /s/ Alan L. Rivera
                                           -------------------------------------
                                           Name:  Alan L. Rivera
                                           Title: Assistant Secretary


                                        ESP LOCK PRODUCTS, LLC

                                        By: /s/ Alan L. Rivera
                                           -------------------------------------
                                           Name:  Alan L. Rivera
                                           Title: Assistant Secretary


                                        GITS MANUFACTURING COMPANY, LLC

                                        By: /s/ Alan L. Rivera
                                           -------------------------------------
                                           Name:  Alan L. Rivera
                                           Title: Assistant Secretary


                                       -2-
<PAGE>

                                        TURNER ELECTRIC, LLC

                                        By: /s/ Alan L. Rivera
                                           -------------------------------------
                                           Name:  Alan L. Rivera
                                           Title: Assistant Secretary

Accepted and Acknowledged by:


SOCIETE GENERALE,
  as Agent for the Lenders

By:________________________________
   Name:
   Title:


                                       -3-
<PAGE>

                                        TURNER ELECTRIC, LLC

                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:

Accepted and Acknowledged by:


SOCIETE GENERALE,
  as Agent for the Lenders

By: /s/ Steven J. Pischel
   --------------------------------
   Name:  Steven J. Pischel
   Title: Vice President


                                       -3-