TIL I had my router table fence set 3/16" out of square for 8 months
Was cutting dadoes for a built-in bookshelf in Maple Valley and could not get the shelves to sit flat no matter how many shims I used. My buddy Dan came by, laid a square on the fence, and just pointed at the gap without saying a word. Turns out I had been reading the tape from the wrong edge of the blade the entire time, and every dado was slightly tapered because of it. Anyone else catch a mistake like this only after a friend points at it?