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ratchet

1. A pawl, click, or detent, for holding or propelling a ratchet wheel, or ratch, etc.

2. A mechanism composed of a ratchet wheel, or ratch, and pawl. See Ratchet wheel, below, and 2d Ratch. Ratchet brace, a circular wheel having teeth, usually angular, with which a reciprocating pawl engages to turn the wheel forward, or a stationary pawl to hold it from turning backward.

In the cut, the moving pawl c slides over the teeth in one direction, but in returning, draws the wheel with it, while the pawl d prevents it from turning in the contrary direction.

Origin: Properly a diminutive from the same word as rack: cf. F. Rochet. See Ratch, Rack the instrument.