Bosal

It is usually made of braided rawhide and is fitted to the horse in a manner that allows it to rest quietly until the rider uses the reins to give a signal.

[5] When the rider is dismounted, the mecate is not used to tie the horse to a solid object, but rather is used as a lead rope and a form of longe line as needed.

[1] On a finished horse, a bosal with a properly balanced heel knot and mecate generally does not require additional support beyond the headstall.

[6] Less often, the bosal may be further supported by attaching the nose button to the horse's forelock or the crownpiece of the headstall, using a single thin strap of leather called a frentera.

Those who advocate use of the bosal-style hackamore note that many young horses' mouths are too sensitive for a bit because they are dealing with tooth eruption, replacing primary molars with permanent teeth.

The classic vaquero and modern practitioners of the "California" cowboy tradition started a young horse in a bosal hackamore, then over time moved to ever-thinner and lighter bosals, then added a spade bit, then eventually transitioning to a spade alone, ridden with romal style reins, often retaining a light "bosalito" without a mecate.

The combination of fiador with either a frentera or a standard headstall or hanger with browband stabilizes the bosal by supporting it with multiple attachment points.

An intermediate-level rawhide bosal on leather headstall, showing attached mecate of synthetic rope and no fiador.
A pencil bosal worn under the bridle on a finished "two rein" horse
Three different sizes of bosals for horses in various stages of hackamore training, the thickest (left) is for starting unbroke young horses, the middle is a medium-sized design for horses that are steady under saddle but still "green", often also used for show, and the thinnest (right) is for use on a polished hackamore horse as it transitions into a bit, designed to be worn under a bridle.