horseshoe

A piece of flat, U-shaped iron that is attached to a horse's hoof. Horseshoes are nailed to the hard surface of the bottom of the hoofs, reducing the risk of injury or wearing down, and allowing for long horse rides on a variety of terrains.

Because horseshoes were so ubiquitous at certain points in history, their shape provided the nomenclature for elements in the natural environment. For example, sharp turns in trails, roads, and rivers have been called oxbows, doglegs, and horseshoe bends.