Surefire Marking Gauge

Screwing plywood pieces with drywall-type screws is quick and easy,
but drilling holes in a straight line can be tricky. That's why I made
this handy little marking gauge that allows me to quickly and
accurately mark a line on my plywood for drilling screw holes. To make
it, simply cut a 3/8 in. by 3/8-in. rabbet into a board that is about
1-in. wide by 8-in. long. You now have a marking gauge to make a line
that will put your screws exactly in the centered edge of your 3/4-in.
plywood.