When you need an accurate square in the 2- to 3-ft. range, your options are limited. Drywall squares are notoriously inaccurate and cumbersome. Carpenter squares involve that nagging hassle of having to hook them onto the edge of your workpiece. If you have a drafting square lying around, drag it out to the shop. Or, go to an art supply store and pick one up ($5 or more). They’re very accurate and you’ll find yourself grabbing it nearly as often as you do the tape measure.