Horseshoe

Device attached to a horse's hoof to protect it from wear

A horseshoe is a piece of equestrian equipment that protects a horse hoof from wear. Shoes are attached on the palmar surface (ground side) of the hooves, usually nailed through the insensitive hoof wall, anatomically akin to the human toenail. Horseshoes can also be glued in certain situations.

From Wikipedia, under CC BY-SA. More on occurri.