I was pulling out some plywood and melamine scraps tonight for some small sled making. Obviously, the base of the sled ought to be flat as possible. Since these offcuts had been sitting around for a while in my garage, I took out my straightedge and feeler gauges to choose the flattest pieces. Naturally this progressed to a machinist-like obsession for flatness. I can't be the only one.*
What's your personal tolerance for sheet good flatness?