Hackamore
The mechanical hackamore works like a double bridle. The only thing you don't do with the reins is on the mouth and tongue, but on the poll, the horse's nose and the chin nerve. Therefore, this bitless bridle is more for experienced riders who ride independently of the reins, because just because your horse doesn't have a bit in its mouth doesn't mean that the hackamore is automatically gentler. A hackamore is usually ridden with loose reins and one-handed.
