 In the Texas tradition, where the bosal is placed low on the horse's face, as well as on very green horses in both the California "vaquero" and Texas traditions, the fiador is used to stabilize the bosal by attaching it to the headstall along the poll joint behind the ears, running under the jaw, and attaching to the bosal at the heel knot, along with the mecate.In the California "vaquero" tradition, the fiador is omitted once the horse is able to work without it; in other traditions the fiador is retained.The word bosal is from the Spanish "bosal" , also spelled "bozal" , meaning muzzle.