EXHIBIT 3.20

   STATE OF DELAWARE
  SECRETARY OF STATE
DIVISION OF CORPORATIONS
FILED 12:30 PM 11/12/1992
  732317025 - 2315670

                          CERTIFICATE OF INCORPORATION

                                       OF

                             FEL-PRO MANAGEMENT CO.

      FIRST: The name of the corporation is Fel-Pro Management Co. (the
"Corporation").

      SECOND: The address of the Corporation's registered office in the State of
Delaware is 1209 Orange Street, Wilmington, Delaware 19801 in the county of New
Castle. The name of the Corporation's registered agent is The Corporation Trust
Company.

      THIRD: The nature of the business or purposes to be conducted or promoted
is to engage in any lawful act or activity for which corporations may be
organized under the General Corporation Law of Delaware (the "GCL").

      FOURTH: The total number of shares of capital stock which the Corporation
shall have authority to issue is 3,000 shares of common stock, par value $.01
per share.

      FIFTH: The name and mailing address of the Corporation's incorporator is:

      Name                          Mailing Address
      ----                          ---------------

      Karen S. McDonald             c/o Katten Muchin & Zavis
                                    525 West Monroe Street
                                    Suite 1600
                                    Chicago, Illinois 60661-3693

      SIXTH: The Board of Directors of the Corporation is expressly authorizeds
to adopt, amend or repeal the by-laws of the Corporation (the "By-Laws").

      SEVENTH: Elections of directors need not be by written ballot unless
otherwise provided in the By-Laws.

      EIGHTH: Whenever a compromise or arrangement is proposed between the
Corporation and its creditors or any class of them and/or between the
Corporation and its stockholders or any class of them, any court of equitable
jurisdiction within the State of Delaware may, on the application in a summary
way of the Corporation or on the application of any receiver or receivers
appointed for this Corporation under the provisions of Section 291 of Title 8 of
the GCL or on the application of trustees in dissolution or of any receiver or
receivers appointed for the Corporation under the provisions of Section 279 of
Title 8 of the GCL, order a meeting of the creditors or class of creditors,
and/or of the stockholders or class of stockholders of the Corporation, as the
case may be, to be summoned in such manner as the said court directs. If a
majority in number representing three-fourths in


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value of the creditors or class of creditors, and/or of the stockholders or
class of stockholders of the Corporation, as the case may be, agree to any
compromise or arrangement and to any reorganization of the Corporation as a
consequence of such compromise or arrangement, the said compromise or
arrangement and the said reorganization shall, if sanctioned by the court to
which the said application has been made, be binding on all the creditors or
class of creditors, and/or on all the stockholders or class of stockholders, of
the Corporation, as the case may be, and also on this Corporation.

      NINTH: The personal liability of the directors of the Corporation is
hereby eliminated to the fullest extent permitted by the GCL.

      TENTH:

      (a)   The Corporation shall to the fullest extent permitted by the GCL,
            indemnify any person who was or is a party or is threatened to be
            made a party to any threatened, pending or completed action, suit or
            proceeding, whether civil, criminal, administrative or investigative
            (other than an action by or in the right of the Corporation) by
            reason of the fact that such person is or was a director or officer
            of the Corporation, or is or was serving at the request of the
            Corporation as a director or officer of another corporation,
            partnership, joint venture, trust or other enterprise, against
            expenses (including attorneys' fees), judgements, fines and amounts
            paid in settlement actually and reasonably incurred by such person
            in connection with such action, suit or proceeding if such person
            acted in good faith and in a manner such person reasonably believed
            to be in or not opposed to the best interests of the Corporation,
            and, with respect to any criminal action or proceeding, had no
            reasonable cause to believe such person's conduct was unlawful. The
            termination of any action, suit or proceeding by judgement, order,
            settlement, conviction, or upon a plea of nolo contendere or its
            equivalent, shall not, of itself, create a presumption that the
            person did not act in good faith and in a manner which such person
            reasonably believed to be in or not opposed to the best interests of
            the Corporation, and, with respect to any criminal action or
            proceeding, had reasonable cause to believe that such person's
            conduct was unlawful.

      (b)   The Corporation shall indemnify any person who was or is a party or
            is threatened to be made a party to any threatened, pending or
            completed action or suit by or in the right of the Corporation to
            procure a judgement in its favor by reason of the fact that such
            person is or was a director or officer of the Corporation, or is or
            was serving at the request of the Corporation as director or officer
            of another corporation, partnership, joint venture, trust or other
            enterprise against expenses (including attorneys' fees) actually and
            reasonably


                                       -2-

 
            incurred by him in connection with the defense or settlement of such
            action or suit if such person acted in good faith and in a manner
            such person reasonably believed to be in or not opposed to the best
            interests of the Corporation and except that no indemnification
            shall be made in respect of any claim, issue or matter as to which
            such person shall have been adjudged to be liable to the Corporation
            unless and only to the extent that the Court of Chancery or the
            court in which such action or suit was brought shall determine upon
            application that, the circumstances of the case, such person is
            fairly and reasonably entitled to indemnity for such expenses which
            the Court of Chancery or such other court shall deem proper.

      (c)   To the extent that a director or officer of the Corporation has been
            successful on the merits or otherwise in defense of any action, suit
            or proceeding referred to in Article TENTH (a) and (b), or in
            defense of any claim, issue or matter therein, such person shall be
            indemnified against expenses (including attorneys' fees) actually
            and reasonably incurred by such person in connection therewith.

      (d)   Any indemnification under Article TENTH (a) and (b) (unless ordered
            by a court) shall be made by the Corporation only as authorized in
            the specific case upon a determination that indemnification of the
            director or officer is proper in the circumstances because such
            director or officer has met the applicable standard of conduct set
            forth in Article TENTH (a) and (b). Such determination shall be made
            (1) by the board of directors by a majority vote of a quorum
            consisting of directors who were not parties to such action, suit or
            proceeding, or (2) if such a quorum is not obtainable, or, even if
            obtainable a quorum of disinterested directors so directs, by
            independent legal counsel in a written opinion, or (3) by the
            stockholders of the Corporation.

      (e)   Expenses incurred by a director or officer in defending a civil or
            criminal action, suit or proceeding shall be paid by the Corporation
            in advance of the final disposition of such action, suit or
            proceeding upon receipt of an undertaking by or on behalf of such
            director or officer to repay such amount if it shall ultimately be
            determined that such director or officer is not entitled to be
            indemnified by the Corporation as authorized in this Article TENTH.

      (f)   The indemnification and advancement or expenses provided by, or
            granted pursuant to, the other subsections of this Article TENTH
            shall not be deemed exclusive of any other rights to which those
            seeking indemnification or advancement or expenses may be entitled
            under any by-law,


                                       -3-

 
      agreement, vote of stockholders or disinterested directors or otherwise,
      both as to action in a director's or officer's official capacity and as to
      action in another capacity while holding such office.

(g)   The Corporation shall have power to purchase and maintain insurance on
      behalf of any person who is or was a director, officer, employee or agent
      of the Corporation, or is or was serving at the request of the Corporation
      as a director, officer, employee or agent of another corporation,
      partnership, joint venture, trust or other enterprise against any
      liability asserted against such person and incurred by such person in any
      such capacity, or arising out of such person's status as such, whether or
      not the Corporation would have the power to indemnify such person against
      such liability under the provisions of this Article TENTH.

(h)   The provisions of this Article TENTH shall be deemed to be a contract
      between the Corporation and each director and officer who serves in such
      capacity at any time while this Article TENTH is in effect and any repeal
      or modification of this Article TENTH shall not affect any rights or
      obligations then existing with respect to any state of facts then or
      theretofore existing or any action, suit or proceeding theretofore or
      thereafter brought or threatened based in whole or in part upon such state
      of facts. The provisions of this Article TENTH shall not be deemed to be a
      contract between the Corporation and any directors or officers of any
      other Corporation (the "Second Corporation") which shall merge into or
      consolidate with this Corporation when this Corporation shall be the
      surviving or resulting Corporation, and any such directors and officers of
      the Second Corporation shall be indemnified to the extent required under
      the GCL only at the discretion of the board of directors of this
      Corporation.

(i)   The indemnification and advancement of expenses provided by, or granted
      pursuant to, this Article TENTH shall, unless otherwise provided when
      authorized or ratified, continue as to a person who has ceased to be a
      director or officer of the Corporation and shall inure to the benefit of
      the heirs, executors, and administrators of such a person.


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      The undersigned incorporator hereby acknowledges that the foregoing
certificate of incorpration is such incorporator's act and deed and that the
facts stated therein are true.


Dated: November 11, 1992                  /s/ Karen S. McDonald
                                          -------------------------------
                                          Karen S. McDonald, Incorporator
                                          c/o Katten Muchin & Zavis
                                          525 West Monroe Street
                                          Suite 1600
                                          Chicago, Illinois 60661-3693


                                       -5-

 
   STATE OF DELAWARE
  SECRETARY OF STATE
DIVISION OF CORPORATIONS
FILED 10:00 AM 02/10/1993
  930415260 - 2315670

                            CERTIFICATE OF CORRECTION
                            FILED TO CORRECT CERTAIN
                  ERRORS IN THE CERTIFICATE OF INCORPORATION OF

                             FEL-PRO MANAGEMENT CO.

          FILED IN THE OFFICE OF THE SECRETARY OF STATE OF DELAWARE ON
                                NOVEMBER 12, 1992

      Fel-Pro Management Co., a corporation organized and existing under and by
virtue of the General Corporation Law of the State of Delaware,

DOES HEREBY CERTIFY:

1.    The name of the corporation is Fel-Pro Management Co.

2.    That a Certificate of Incorporation was filed with the Secretary of State
      of Delaware on November 12, 1992 and that said Certificate requires
      correction as permitted by Section 103 of the General Corporation Law of
      the State of Delaware.

3.    The inaccuracies of said Certificate to be corrected are as follows:

            (a) The number of authorized shares was incorrectly stated as 3,000
            shares of capital stock instead of 11,000 shares of capital stock;
            and (b) said Certificate inadvertantly neglected to provide for
            cumulative voting in all elections for directors.

4.    Article Fourth of the Certificate of Incorporation is corrected to read as
      follows:

            Article Fourth: The total number of shares of capital stock which
            the Corporation shall have authority to issue is 11,000 shares of
            common stock, par value of $.01 per share.

5.    Article Seventh of the Certificate of Incorporation is corrected to read
      as follows:

            Article Seventh: Directors shall be elected at the annual meeting of
            stockholders. In all election for directors, every stockholder shall
            have the right

 
            to vote the number of shares owned by such stockholder for as many
            persons as there are directors to be elected, or to cumulate such
            votes, and give one candidate as many votes as shall equal the
            number of directors multiplied by the number of such shares or to
            distribute such cumulative votes in any proportion among any member
            of candidates. Elections of directors need not be by written ballot
            unless otherwise provided in the By-laws."

      IN WITNESS WHEREOF, FEL-PRO MANAGEMENT CO. has caused this Certificate of
Correction to be signed and attested to this 18th day of December, 1992.

                                  FEL-PRO MANAGEMENT CO.


                                  Name: /s/ Kenneth G. Lehman
                                       ----------------------

                                  Title: Co-Chairman of the Board
                                       --------------------------

Attest:


Name: /s/ [ILLEGIBLE]
     ----------------
Title: Asst. Secretary
      ----------------