Uses
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. While designed for use on young horses, Bosals are equipment intended for use by experienced trainers and should not be used by beginners, as they can be harsh in the wrong hands.
The bosal is ridden with two hands, and uses direct pressure, rather than leverage. It is particularly useful for encouraging flexion and softness in the young horse, though it has a design weakness that it is less useful than a snaffle bit for encouraging lateral flexion.
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. This process took many years and required an expert trainer. The "Texas" tradition cowboy, and most modern trainers, will often start a young western riding horse in a bosal, but then move to a snaffle bit, then to a simple curb bit, and may never introduce the spade at all. Other trainers start a horse with a snaffle bit, then once lateral flexion is achieved, move to a bosal to encourage flexion, then transition to a curb. However, this sequence is frowned upon by those who use classic vaquero techniques.
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. However, it also limits the action of the bosal, and thus, particularly in the California tradition, is removed once the horse is comfortable under saddle. On a finished horse, a bosal with a properly balanced heel knot and mecate generally does not require these additions.
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.
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