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Exhibit (a)(4)
 (COMPUTERSHARE LOGO)   Voting Instruction Form (VIF)  Special Meeting to be held on February 18, 2005   NON-REGISTERED (BENEFICIAL) SHAREHOLDERS
 1.
    
    We are sending to you the enclosed proxy-related materials that relate to a meeting of the
holders of the series or class of securities that are held on your behalf by the intermediary
identified above. Unless you attend the meeting and vote in person, your securities can be
voted only by management, as proxyholder of the registered holder, in accordance with your
instructions.2.
    
    We are prohibited from voting these securities on any of the matters to be acted upon at the
meeting without your specific voting instructions. In order for these securities to be voted
at the meeting, it will be necessary for us to have your specific voting instructions. Please
complete and return the information requested in this VIF to provide your voting instructions
to us promptly.3.
    
    Every shareholder has the right to appoint some other person of their choice, who need not be
a shareholder, to attend and act on their behalf at the meeting. If you wish to appoint a
person other than the persons whose names are printed herein, please insert the name of your
chosen appointee in the space provided (see reverse).4.
    
    This VIF should be signed by you in the exact manner as your name appears on the VIF. If
these voting instructions are given on behalf of a body corporate set out the full legal name
of the body corporate, the name and position of the person giving voting instructions on
behalf of the body corporate and the address for service of the body corporate.5.
    
    If this VIF is not dated, it will be deemed to bear the date on which it is mailed by
management to you.6.
    
    When properly signed and delivered, securities represented by this VIF will be voted as
directed by you, however, if such a direction is not made in respect of any matter, the VIF
will direct the voting of the securities to be made as recommended by management in the
Management Information Circular for the meeting.7.
    
    This VIF confers discretionary authority on the appointee to vote as the appointee sees fit
in respect of amendments or variations to matters identified in the notice of meeting or other
matters as may properly come before the meeting or any adjournment thereof.8.
    
    Should you wish to attend the meeting and vote in person, please write your name in the place
provided for that purpose in this VIF and we will send to you a form of legal proxy which will
grant you the right to attend the meeting and vote in person. If you require assistance in
that regard, please contact the Registered Representative who services your account .9.
    
    Your voting instructions will be recorded on receipt of the VIF and a legal form of proxy
will be submitted on your behalf.10.
    
    By providing voting instructions as requested, you are acknowledging that you are the
beneficial owner of, and are entitled to instruct us with respect to the voting of, these
securities.11.
    
    If you have any questions regarding the enclosed documents, please contact the
Registered Representative who services your account.12.
    
    This VIF should be read in conjunction with the accompanying Management Information Circular. VOTE USING THE TELEPHONE OR INTERNET 24 HOURS A DAY 7 DAYS A WEEK! Voting by mail
 Voting by mail or by Internet
  (VOTE USING THE TELEPHONE)  
    
    Call the toll free number listed BELOW from a touch tone
telephone. There is NO CHARGE for this call.1 8XX XXX-XXXX
    
    Voting Instructions must be received by 5:00 pm, Eastern Time, February 17, 2005.
  (VOTE USING THE INTERNET)  
    
    Go to the following web site:
www.computershare.com/ca/proxy/masonite
    
    Voting Instructions must be received by 5:00 pm, Eastern Time, February 17, 2005.
 
   To vote by telephone or the Internet, you will need to provide your HOLDER ACCOUNT NUMBER and ACCESS NUMBER listed below. HOLDER ACCOUNT NUMBER  C1234567890          ACCESS NUMBER  12345 If you vote by telephone or the Internet, DO NOT mail back this VIF.  005DXA




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(GRAPHICS) Appointee(s)I/we being
holders of the Corporation hereby appoint
Peter A. Crossgrove, Chairman, or, failing him, Howard Beck
    
    OR
    
    Print the name of the person you are appointing if this person is someone
other than the Management Appointee(s).
 Resolution Management recommends a vote FOR the following resolution. Please read the resolution in full in the accompanying Management Information Circular. For
    
    Against
    
    Abstain1
    
    A special resolution (the Arrangement Resolution) approving the arrangement of Masonite
under section 182 of the Business Corporations Act (Ontario).
    
    4
    
    o
    
    o
    
    oThe full text of the Arrangement
Resolution is set out on Appendix A to the Management
Information Circular dated January 18, 2005 (the Circular) with respect to the Meeting,
as such Arrangement Resolution may be amended or varied at the Meeting.
  Signature(s)/Authorized
Officer(s)  Sign Here  This section must be completed for your instructions to be executed.  Signature(s) Day
    (GRAPHICS)