Whenever I install door or window casings, I use the jig shown here to make sure that I get an accurate 1/4-in. reveal. It’s made of two square pieces of hardwood, 1/4 in. thick, that are glued together with a 1/4-in. offset. This jig has so many corners that half the time I grab it out of my nail bag it’s in the right position for use.
John Sandstrom, Fort Dodge, IA