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.

These D - Shackles are designed and rated for in-line tension, they should not be side loaded, as side loading can twist or bend the bow of the shackle.