Detent

n.

1.

(Mech.) That which locks or unlocks a movement; a catch, pawl, or dog; especially, in clockwork, the catch which locks and unlocks the wheelwork in striking.

Noun

1.

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

catch, click, dog, pawl, rachet, ratch, ratchet, stop