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                                                                  Exhibit 99.1


                                FOURTH AMENDMENT
                                       to
                 RIGHTS AGREEMENT DATED AS OF NOVEMBER 25, 1986
                 ----------------------------------------------

          THIRD AMENDMENT (the "Amendment") dated as of March 14, 1996 to the
Rights Agreement dated as of November 25, 1986, as amended (the "Rights
Agreement"), between Bird Corporation (the "Company") and American Stock
Transfer & Trust Company (the "Rights Agent").

                                   WITNESSETH:

                WHEREAS, the Company intends to enter into an Agreement and Plan
of Merger dated as of March 15, 1996 (the "Merger Agreement") with CertainTeed
Corporation, a Delaware corporation ("CertainTeed"), and BI Expansion
Corporation, a Massachusetts corporation ("Acquisition Sub") and a wholly owned
subsidiary of CertainTeed, pursuant to which (i) Acquisition Sub will merge with
and into the Company, which will thereby become a wholly owned subsidiary of
CertainTeed, and (ii) the Company's shareholders (other than shareholders who
perfect appraisal rights) will be entitled to receive the consideration provided
in the Merger Agreement;

                WHEREAS, the Company has determined that this Amendment shall
not adversely affect the interests of the holders of the Rights Certificates;

                WHEREAS, the Company and the Rights Agent desire to amend the
Rights Agreement in accordance with Section 26 thereof and this Amendment;

                WHEREAS, it is contemplated that this Amendment be executed by
the Company and the Rights Agent before the Company enters into the Merger
Agreement;

                NOW, THEREFORE, in consideration of the premises and mutual
agreements set forth in the Rights Agreement and this Amendment, the parties
hereto agree as follows:

                1.    The Rights Agreement is hereby amended by adding the
following new section after Section 32 thereof:

                      "Section 33. CERTAINTEED MERGER. Notwithstanding anything
          to the contrary herein, neither CertainTeed Corporation, a Delaware
          corporation ("CertainTeed"), nor BI Expansion Corporation, a
          Massachusetts corporation ("Acquisition Sub"), shall be 








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          considered an Acquiring Person under this Agreement and no Stock
          Acquisition Date, Triggering Event or Distribution Date has occurred
          or will occur, in any such case as a result of the approval, execution
          or delivery of, or consummation of the transactions set forth in the
          Agreement and Plan of Merger dated as of March 15, 1996 by and among
          the Company, CertainTeed and Acquisition Sub; PROVIDED, HOWEVER, that
          in the event that CertainTeed or Acquisition Sub or any affiliate of
          CertainTeed becomes the Beneficial Owner of any shares of Common Stock
          otherwise than pursuant to such Merger Agreement the provisions of
          this sentence (other than this proviso) shall not be applicable to
          such shares of Common Stock which CertainTeed or Acquisition Sub or
          any affiliate of CertainTeed so otherwise became the Beneficial
          Owner."

                2. Exhibit A to the Rights Agreement is hereby amended by adding
", as amended" after "dated as of November 25, 1986" in the sixth line of
thereof.

                3. Exhibit B to the Rights Agreement is hereby amended by adding
the following paragraph before the last paragraph thereof:

                      "Notwithstanding anything to the contrary in the Rights
          Agreement, neither CertainTeed Corporation, a Delaware corporation
          ("CertainTeed"), nor BI Expansion Corporation, a Massachusetts
          corporation ("Acquisition Sub"), will be considered an Acquiring
          Person under the Rights Agreement Agreement and no Stock Acquisition
          Date, Triggering Event or Distribution Date has occurred or will
          occur, in any such case as a result of the approval, execution or
          delivery of the Agreement and Plan of Merger dated as of March 15,
          1996 by and among the Company, CertainTeed and Acquisition Sub;
          PROVIDED, HOWEVER, that in the event that CertainTeed or Acquisition
          Sub or any affiliate of CertainTeed becomes the Beneficial Owner of
          any shares of Common Stock otherwise than pursuant to such Merger
          Agreement the provisions of this sentence (other than this proviso)
          shall not be applicable to such shares of Common Stock which
          CertainTeed or Acquisition Sub or any affiliate of CertainTeed so
          otherwise became the Beneficial Owner."


                4. Exhibit B to the Rights Agreement is hereby amended by
deleting the last paragraph thereof and replacing it 











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with the following:

                      "A copy of the Rights Agreement and each of the amendments
          thereof have been filed with the Securities and Exchange Commission. A
          copy of the Rights Agreement and each of the amendments thereof are
          available free of charge from the Company. This summary description of
          the Rights does not purport to be complete and is qualified in its
          entirety by reference to the Rights Agreement, as amended, which is
          hereby incorporated herein by reference."

                5. The term "Agreement" as used in the Rights Agreement shall be
deemed to refer to the Rights Agreement as amended to the date hereof.

                6. This Amendment shall be deemed to be a contract made under
the laws of the Commonwealth of Massachusetts and for all purposes shall be
governed by and construed in accordance with the laws of such Commonwealth
applicable to contracts to be made and performed entirely with such
Commonwealth.

                7. This Amendment may be executed in any number of counterparts,
each of which shall be deemed an original, but all of which together shall
constitute one and the same instrument.

                IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed by their duly authorized officers as of the date first
written above.





                                         BIRD CORPORATION


                                         By:   /s/ Joseph D. Vecchiolla
                                               -------------------------------
                                               Name:  Joseph D. Vecchiolla
                                               Title: Chairman


                                         AMERICAN STOCK TRANSFER & TRUST COMPANY


                                         By:   /s/ Herbert J. Lemmer
                                               -------------------------------
                                               Name:  Herbert J. Lemmer
                                               Title: Vice President