Overcheck

The modern overcheck is often a necessary piece of safety equipment for certain types of harness and is an aid to the driver in keeping a horse's head properly positioned.

An overcheck has a practical purpose; if a horse lowers its head too far when in harness, particularly if moving quickly, it can catch the bridle or reins on the shafts of the carriage or wagon, risking an accident.

On a hard-working draft horse, it generally is not used at all, as it puts the animal off balance by preventing it from lowering its head when trying to pull significant weight.

If an overcheck is inappropriately used, or used for too long a period, spinal strain resulting in neck or back injury can occur.

Historically, improper use and overuse created chronic problems with the spine and back that in some cases made certain horses useless as working animals.

Side reins are a very common training tool for working horses on the longe, also considered standard safety equipment in the sport of equestrian vaulting, but rarely if ever are used by a mounted rider.