Feeler Gauges - 0.12mm, 0.16mm 0.20mm 0.40mm 0.80mm & 1.60mm

thingiverse

Obviously their accuracy will be quite low, as they likely won't print at the exact heights they're designed for. However, they can still be used for very precise measurements and fitting; as they're useful in measuring gaps which are difficult to reach with only a set of calipers. Simply stack multiple gauges to fit into the gap and then use calipers to measure the stack. For printing, you will need to use a layer height of 0.12mm or smaller. Keep in mind, that you need a print bed that you can easily remove very thin prints from; as the thinner gauges will be difficult to remove without mangling them.