One inch is equal to 25.4 mm

Feeler gauges are used:
– To check the gap between the mating parts
– To check and set the spark plug gaps
– To set the clearance between the fixture (setting block) and the cutter/tool for machining the jobs
– To check and measure the bearing clearance, and for many other purposes where a specified clearance must be maintained.

A try- square is a woodworking tool used for marking and measuring a square piece of wood. The square refers to the tool's primary use of measuring the accuracy of a right angle (90 degree angle); to try a surface is to check its straightness or correspondence to an adjoining surface.