Sure Cure for Miter-Joint Double-Bypass
It can be tough to make great-looking miter joints because it seems like one piece is always trying to sneak past the other during clamping. These handy corner-clamping blocks eliminate this bypass problem.I place one of these blocks between the clamp and the workpiece in each corner, as shown above, and tighten the clamps. The blocks protect your workpieces and hold them in perfect 90° alignment to ensure a square assembly.
—Chuck Hedlund, WOOD® magazine staff