Feeler gauge is a measuring tool, mainly used for measuring gap spacing. It is a gauge composed of a group of thin steel sheets with different thickness differences. Feeler gauge is used to measure gap size. When checking whether the measured size is qualified, this method can be used to judge, or the inspector can judge according to the tightness of the fit between the feeler gauge and the measured surface. Our feeler gauge series includes different combinations, including feeler gauges, rail gap gauges, and steel plate rulers with different ranges, which can be used together.