A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.
1910, Victor Appleton, Tom Swift and his Motorcycle
A pawl is a sort of catch that fits into a ratchet wheel and pushes it around, or it may be used as a catch to prevent the backward motion of a windlass or the wheel on a derrick.
1994, Cormac McCarthy, The Crossing:
The nails in the rim of the wheel went ratcheting over the leather pawl and the wheel slowed and came to a stop and the woman turned to the crowd and smiled.