Breastcollars are pieces of tack used in horseback riding to help secure the saddle in place and prevent it from slipping back on the horse's body. They are typically made of leather or nylon and consist of a strap that runs across the horse's chest and attaches to the saddle's girth or cinch. Breastcollars are commonly used in English riding disciplines such as dressage, show jumping, and eventing to provide additional stability and control over the horse.