Ozark double link leather curb strap. Russet leather, 5/8".
The curb chain applies pressure to the curb groove under a horse's chin when the curb rein of the bit is used. When the curb rein is pulled, the shank of the bit rotates back towards the chest of the horse and the cheek (upper shank) of the bit rotates forward (since it is a lever arm). The curb strap used on a snaffle does not increase the leverage but is used to help balance the bit in the horse’s mouth and keep it centered.