 While mechanical hackamores made entirely of leather with short shanks can be relatively mild, the addition of a longer shank and chain or metal under the jaw or over the nose can make this device a very severe piece of equipment that borders on animal abuse, thus making the device quite controversial in some equestrian circles.If adjusted too low, it can also put excessive pressure on the horse's nose cartilage, possibly even breaking it, and low placement may also obstruct the horse's breathing.In cases of a severe mechanical hackamore with long shanks, abusive use has been claimed to risk breaking the horse's jaw.