rachet
noun
rach·et
less common spelling of ratchet
1
: a mechanism that consists of a bar or wheel having inclined teeth into which a pawl drops so that motion can be imparted to the wheel or bar, governed, or prevented and that is used in a hand tool (such as a wrench or screwdriver) to allow effective motion in one direction only
2
: a pawl or detent for holding or propelling a toothed wheel