Even if you own a table saw, sometimes it's easier to rip large sheets of plywood with a circular saw. The trick to a perfectly straight cut is to clamp a straightedge to the plywood and use it as a guide for your saw. On most circular saws, the distance between the edge of the saw's base and the blade is 1-1/2 in., so you can simply position the straightedge 1-1/2 in. from your cutting line. But measure this distance on your saw to be sure.

You can buy a straightedge or use the factory edge of a plywood sheet. If your straightedge only has one straight edge, be sure to mark it to avoid using the crooked side.