I had to install some cabinet-grade plywood over a pair of recessed light fixtures, and I wanted to make sure the holes ended up in exactly the right spots. I did it by first skim-coating the backside of the plywood with some water-based putty (joint compound would also work). Then I lifted the piece into position against the light canisters and gave it a push to record their outlines. Perfect circles were impressed in the putty. Then it was easy to find the centers of the circles, scrape away the putty and make my cuts.
Barney Potratz, Fairfield, IA
