Once again this is a question of tolerance. It could be a place you only care about minimum clearance. If the spec is for a gap of at least 15 mil then a pack of 30 mil key cards makes for a bunch of cheap easily replacable go/nogo gauges with enough leway that even a worn one won’t put you under spec.
I’m most familiar with IPC standards for electronics but even in the most critical class 3 applications there are plenty of spots where the standards are effectively gauged by eyeball let alone with even a makeshift tool because those specific specs aren’t that critical for the application.