Years ago I bought a set of machinist alphabet stamps at a garage sale that I use to identify parts. Currently I'm working on a set of three tables that are mortised and tenoned, legs to aprons. That's a total of 24 parts, hand fitted parts! You can easily stamp the tenon on a cheek and an area by the mortise that will get covered when assembled. Unlike triangular marks, pencil, or chalk these stamps won't come off.