The cheek-to-shank angle also varies, with some straight up and down, others with the shanks curving backward. Some shanks have a dramatic S-curve. Cheek angle influences the angle at which the bit engages and thus way the horse carries its head. Therefore, the type of shank needs to be considered according to the use of the horse. Horses that maintain a more vertical head position, such as dressage horses and western horses trained in the "straight up" or "Vaquero" tradition generally use a curb bit with straighter shanks. Those that have a nose-out head position when working, such as cutting and roping horses, more commonly use a more curved shank. Shanks on certain western bits that curve back are sometimes called a "grazing bit." Though a horse should never be allowed to graze in a bridle, the term came from the mistaken notion that the turned-back shank was to allow the horse to eat with a bridle. In reality, the design simply allowed the horse to comfortably travel with its nose well ahead of the vertical. An S curve in a shank does not have a major effect on the angle at which the rein engages, but may alter the balance of the bit at the point the lever arm joins the mouthpiece.