mechanical device - mechanism consisting of a device that works on mechanical principles

detent, pawl, click, dog - a hinged catch that fits into a notch of a ratchet to move a wheel forward or prevent it from moving backward

ratchet wheel - toothed wheel held in place by a pawl or detent and turned by a lever

ratchet screwdriver, spiral ratchet screwdriver - a screwdriver with a ratchet (so the blade turns in only one direction) and a spiral in the handle (so the blade rotates) with downward pressure on the handle