Blocks put the squeeze on out-of-square cases

We all know that to square up carcases you place a clamp across the unit, spanning the longer of the two diagonal measurements. Sometimes that's easier said than done because the clamp doesn't stay put.

To assist matters, make a pair of 2×4 clamping blocks. Form an arrowhead on one end of each block by making two 45° cuts. Then cut a dado and groove as shown, each wide enough for your project material, and about ³⁄₄ " deep. Place the blocks and clamp as shown to controllably draw the carcase into square.
—Ed Swakon, West Linn, Ore.