Shackle

Specifications:

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.

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.