Middle English schakel, from Old English sceacul; akin to Old Norse skǫkull pole of a cart
- 1: something (as a manacle or fetter) that confines the legs or arms
- 2: something that checks or prevents free action as if by fetters —usually used in plural
- 3: a usually U-shaped fastening device secured by a bolt or pin through holes in the end of the two arms
- 4: a length of cable or anchor chain of usually 15 fathoms
A shackle, also known as a gyve, is a U-shaped piece of metal secured with a clevis pin or bolt across the opening, or a hinged metal loop secured with a quick-release locking pin mechanism. The term also applies to handcuffs and other similarly conceived restraint devices that function in a similar manner.
Shackles are the primary connecting link in all manner of rigging systems, from boats and ships to industrial crane rigging, as they allow different rigging subsets to be connected or disconnected quickly. A shackle is also the similarly shaped piece of metal used with a locking mechanism in padlocks. A carabiner is a variety of shackle used in mountaineering.