I needed some 3 inch squares cut from 1/4 inch plywood. I had access to a Black & Decker Workmate and a circular handsaw, but not to a table saw or a radial arm saw. Cutting small pieces like that can be dangerous with a circular saw because it is difficult to secure the wood and things can get out of control very soon. I used my Workmate both to secure the wood and to guide the saw safely.
Step 1: Get a true edge
This is some scrap 1/4 inch plywood. Neither of the two edges visible is straight and true. I used my tri-square to mark a straight line so I can trim the plywood for a true edge. See this Instructable
to make this tri-square
Step 2: How much to offset
I needed to measure the distance from the edge of the saw blade to the edge of the saw's shoe or base. It is 1 1/2 inches. That does not include the thickness of the blade, which is a factor in some cuts, but not in others.
Step 3: Position in the Workmate
My piece of plywood is narrow enough that it fits between the two screw assemblies that pull the jaws of the Workmate together. The construction of the Workmate limits the width of material that can be sawn this way, but I am interested in sawing small pieces safely, so the method fits what I need.
I have positioned and clamped the piece of plywood in the Workmate so a little more than 1 1/2 inch extends above the Workmate surface.
Step 4: Saw
The top surface of the Workmate jaws are very straight and true. I rested the edge of the saw's base on the top surface of the Workmate while holding the base as near to exactly vertical as possible. Pull the saw's trigger switch and trim the edge of the plywood. Checking with a straightedge showed the plywood now has a straight and true edge.