Pull roller
In trotting , a pull roller is sometimes used to prevent the horse from kinking its own windpipe while pulling and thus getting no more air.
The roll is usually made of plastic and has a diameter of 6 cm and a length of about 25 cm. It is attached to the horse's bridle in such a way that it hangs across the horse's throat and thus prevents the horse's head from being pushed against the horse's neck. This ensures a minimum of throat clearance, which is necessary to allow a sufficient flow of air through the windpipe.
use
The pull roller is often used on horses that pull very hard and would storm away uncontrollably with loose lines. In order to keep the horse under control in its running speed, the driver holds on to the leashes and thus on the bit in the horse's mouth. If this exhausting pulling between rider and horse is carried out too extreme, it can happen to inattentive riders to pull the horse's head so close to the neck that the windpipe becomes too narrow at first (the horse starts to "whistle") or even completely is constricted. If the horse cannot breathe at all, it will pass out and collapse, which should be avoided.
There are other forms of pull roll that have the same effect.