Rein snaps are sometimes referred to as "Parrot Clips" or "Scissor Clips" because of the shape of the hook, and the way both sides of the hook open. 

As the name suggests, these snaps are often used on reins as an excellent form of quick release where they attach to the bit. 

They are also popular with carriage drivers as a quick release between the crupper backband and driving saddle. 

19mm (3/4") Square Eye code 984517 

25mm (1")  Square Eye  code 984519