Just because a measuring device is not standards referenced does not mean it can not be used to measure.

If I need a peg to match the size of a drill bit, any collection of 12 holes is likely to have one the size of the drill bit that lets me tell my peg maker to "make the pegs this size."

Handymen are just cussed enough* to not label any of them, and to expect the FNG (new guy) to remember which of the 12 unlabeled holes was the one.

* Cussed enough is a slang adjective that describes someone who does things that annoy people. We say it in Texas, but I do not expect everyone uses that phrase. I can not think of a standard term that carries the same connotations.