Feeler Gauge Set in a Folding Handle: Curtin, 1911

Feelers are thin blades of known thickness, used to measure small gaps by feel. Peter A. Curtin of Buffalo patented a pocket set in 1911, US 987,703: blades differing by about a thousandth of an inch (for example 0.002, 0.003, 0.004 and 0.006 in), each marked with its thickness, all pivoted on one screw between the two sides of a handle so they fold away like the blades of a jack-knife. Two or more blades laid side by side measure their combined thickness. The thin blades are flexible enough to be pressed together at their free ends even when they do not lie next to each other at the pivot.