Do-it-yourself cutoff jig uses a circular saw
Clean crosscuts often prove elusive with a hand-held circular saw. It's almost impossible to push a saw perfectly straight, and the offcuts usually fall away leaving raggedy-looking splinters.
Make your own low-cost cutoff jig. Construct the base by gluing and screwing a pair of parallel 1x2s to the top of a piece of 3⁄4 "x12"x4' particleboard. Attach aluminum angle bars at 90° to the 1x2s, and space them the width of your saw's base plate. Adjust the saw so it cuts through the 1x2s, and makes a shallow kerf in the base. To use, simply clamp the saw jig to a workbench, slip your workpiece under the aluminum guide bars, and cut. (If your saw rides rough on the guide bars, a thin film of paraffin wax will help it slide more easily.)
—Michael Covington, Athens, Ga.