Buy: Shackles

: These are narrow and shaped like the letter "D." They are designed strictly for straight-line pulls . Never side-load a D-shackle, as it can twist and fail. Buy shackles & hooks from horntools

: These have a rounded "O" shape. The larger loop allows them to be side-loaded or to hold multiple lines (like a bridle) without crowding the pin. buy shackles

The environment dictates the material and type of shackle you need: : These are narrow and shaped like the letter "D