EXHIBIT 3.23

                          CERTIFICATE OF INCORPORATION

                                       OF

                               MAMMOTH CHINA LTD.

      FIRST: The name of the Corporation is Mammoth China Ltd.

      SECOND: The registered office of the Corporation in the State of Delaware
is located at 1013 Centre Road, City of Wilmington, County of New Castle. The
name and address of its registered agent is Corporation Service Company, 1013
Centre Road, Wilmington, Delaware 19805.

      THIRD: The purpose of the Corporation is to engage in any lawful act or
activity for which corporations may be organized under the General Corporation
Laws of the State of Delaware.

      FOURTH: The total number of shares of stock which the Corporation shall
have authority to issue is Three Thousand (3,000) shares of Common Stock of the
par value of One Cent ($.01) per share.

      FIFTH: The name and mailing address of the incorporator is Michael J.
Sharon; Nortek, Inc.; 50 Kennedy Plaza; Providence, RI 02903.

      SIXTH: The Corporation is to have perpetual existence.

      SEVENTH: Elections of Directors need not be by written ballot unless the
by-laws of the Corporation so provide.

      EIGHTH: In furtherance and not in limitation of the powers conferred by
the laws of the State of Delaware, the Board of Directors of the Corporation is
authorized and empowered to



adopt, alter, amend and repeal the by-laws of the Corporation in any manner not
inconsistent with the laws of the State of Delaware.

      NINTH: Then Corporation shall indemnify its officers, directors, employees
and agents to the fullest extent permitted by the General Corporation Laws of
Delaware.

      TENTH: Meetings of stockholders may be held within or without the State of
Delaware, as the by-laws may provide. The books of the Corporation may be kept
(subject to any statutory provision) outside the State of Delaware at such place
or places as may be designated from time to time by the Board of Directors or in
the by-laws of the Corporation.

      ELEVENTH: The Corporation reserves the right to amend, alter, change or
repeal any provision contained in the Certificate of Incorporation, in the
manner now or hereafter prescribed by statute.

      TWELFTH: A director of the Corporation shall not be liable to the
Corporation or its stockholders for monetary damages for breach of fiduciary
duty as a director, except to the extent such exemption from liability or
limitation thereof is not permitted under the Delaware General Corporation Law
as the same exists or may hereafter be amended. No amendment or repeal of this
Article TWELFTH shall apply to or have any effect on the liability or alleged
liability of any director of the Corporation for or with respect to any acts or
omissions of such director occurring prior to such amendment or repeal.

      I, THE UNDERSIGNED, being the incorporator hereinbefore named, for the
purpose of forming a corporation pursuant to the General Corporation Laws of the
State of Delaware, do make this certificate, hereby declaring and certifying
that this is my act and deed and the facts

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herein stated are true, and accordingly have hereunto set my hand this 20th day
of September, 1999.

                                                 /s/ Michael J. Sharon
                                               ---------------------------
                                                     Michael J. Sharon
                                                     Incorporator

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