Which of these protects a horse's lower leg from an injury that may occur during exercise?

Brushing boots or splint boots are used to protect a horse's legs during exercise, protecting the lower leg from an injury that may occur if one leg or hoof strikes the opposite leg. They are commonly seen on horses in fast work, such as jumping, when in training, such as when longeing, or in competitions such as reining or eventing. Brushing injuries are more common on the forelegs, when one hoof catches the other leg, or when the fetlock or cannon bones hit each other. This can cause a serious injury on a horse's legs, especially if the horse is wearing shoes.