I finally asked the old guy at the lumber yard in Fresno why he taps every board before he buys it
I was picking through a stack of walnut for a set of drawer fronts and this older guy next to me kept knocking on each board with his knuckle before setting it aside. I asked what he was listening for and he just said dry boards ring, wet ones thud, then he handed me one and made me try it. Turns out he was right and the two boards I had already picked both sounded flat, so back on the rack they went. I've been doing that knock test on every board since, and it saved me from a cupped panel last month. Anybody here have a trick like that for spotting boards that will move after you cut them?