If the bit is adjusted too low (not touching the corner of the mouth), it is primarily a safety concern, though the action of the bit can also be altered and lead to discomfort. A horse can get its tongue over a too-low bit and thus evade its pressure, plus the action of the bit is altered and it will not act on the mouth as it was designed. Horses with a bit too low will often open their mouths to evade pressure and may chew on it excessively. In extreme cases, the bridle could even fall off if the rider pulls hard on the reins, hence raising the bit and loosening the cheekpieces, at the same time the horse rubs, tosses or shakes its head vigorously.