What is the feeler used for?

The feeler gauge is one of the measuring instruments used to check the gap.

The feeler gauge is also called micrometer or thickness gauge. Dirt and dust on the feeler gauge and workpiece must be removed before use. When in use, one or several pieces can be overlapped and inserted into the gap, and it is appropriate to feel a slight delay. When measuring, the action should be light, and hard insertion is not allowed. It is also not allowed to measure parts with higher temperature.