horseshoe, narrow plate, commonly of iron or steel, shaped to fit a horse's hoof and attached to the hoof by nailing it to the inner edge of the horny wall of the hoof. Horseshoes vary from the light plate worn by race-horses to the heavy shoe with sharp pointed wedges, or calks, worn by horses of logging camps in drawing heavy loads over roads of ice. The earliest extant shoe dates from the 6th cent. B.C. A horseshoe used by the Romans was a leather boot with a metal plate at the bottom. Before the advent of motor vehicles, shoeing horses was an important trade, often combined with general blacksmithing. Often the horseshoer's skill cured lameness, and before veterinary medicine became a profession the horseshoer, or farrier, treated horses for all their diseases. The horseshoe is an emblem and talisman of good luck.