Rein hook

A rein hook, or rein holder is a device used in chariotry. It is designed to hold the reins in place when the driver is away, or his hands are used for something else than driving. It is used to free the rider's hands. It is held in place by a "charioteer's belt".

Characteristics
"Narrow-back rein holders" were probably hung to the rider's waist. They worked as rein hooks, attached at the belt, for horse control.

"Broad-back rein holders" were probably fixed at the leading edge of the carriage to hold the reins. They may also have been attached at the belt of the charioter for hands-free control.

Rein holders were probably introduced in China circa 1200 BCE, where they first appear at Yinxu, from the Northern Zones, where earlier rein holders are known as far as the Minusinsk basin.