The stirrup is a ring with a flat bottom fixe on a leather strap, usually hung from each side of a saddle by an adjustable strap to create a footrest for a person using a riding animal (usually a horse or other equine, such as a mule), used as a support for the foot of a rider when seated in the saddle and as an aid in mounting. It greatly increases the rider's ability to stay in the saddle and control the mount, increasing the animal's usefulness in communication, transportation and warfare. It is considered one of the basic tools used to create and spread modern civilization. Some argue it is as important as the wheel or printing press.