The message
from "The Medway Handyman" contains
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Circular saw and one of these; http://members.aol.com/woodmiser1/sawbd.htm

You will get a dead accurate clean cut.

Seriously useful, however the one I made had a minor mod. I had another
strip of ply screwed/glued on edge to the double-thickness bit under the
saw. Low enough to clear the back of the motor (or far enough back,
depending which saw I'm using). Made it more rigid, which is an
advantage if you're not working on a nice flat bench. For cutting really
thin ply or hardboard it made quite a difference.

--
Skipweasel
Pay no attention to that man behind the curtain.