Unfortunately fixed gauges (feeler gauges, spark gap tools, profile gauges, wire gauge tools, bolt sizers, etc) didn't make it into any of the top-level categories, so they are lumped in with the mess of "Other Tools": https://www.periodictableoftools.com/Categories/Other.html

Some day I might create some new rows, because there are a lot of important categories that are completely absent.

Depends. They had dial instruments and micrometers, but not like spark “feeler” plug gauges. Also no voltmeters (they had powered equipment though)

Come to think of it, I didn’t notice some of tools you’d need to work on an engine.