Curb bits have shanks that are attached to the mouthpiece and extend to the sides of the face of the horse. At the end of the shank, there are rings where the reins are fastened. That is why, instead of having a direct contact with the horse's mouth, a rider can have an indirect contact through the ends of the shanks. A curb chain is also placed on both sides of the mouthpiece adjacent to the corners of the mouth. Once the horse rider applies pressure on the reins, the curb chain becomes tighter, thus exerting more pressure on the horse's mouth. Curb bits use leverage. This means that the pressure exerted by the rider is multiplied. The horse feels more pressure; therefore, he responds more immediately to the commands of his rider.
With curb bits, it is somehow difficult to communicate with the horse to go left or right. Once the rider pulls on the rein, the curb chain will just tighten the jaw without instructing him the directions. The horse needs to learn to follow commands based on the pressure on his neck and not on his mouth. When he feels the pressure on his left neck caused by the rein, he must move to the right, and vice versa. The complicated way to convey a message to the animal is one of the reasons why only professional, trained and expert horse riders use curb bits.
Another reason, as mentioned, is the severity of the curb horse bits. Nevertheless, the severity of this bit is based on different conditions. For one, if the shank is longer than the average, more leverage is created. If the curb chain is also tighter, the horse will most likely feel more pressure. However, if the curb chain is loose, the horse will not be able to feel the pressure immediately. Lastly, the size of the port influences the severity of the curb bit. The pressure is greater if the port is higher.
These horse bits must, once again, be used by professional and well-trained horse riders. Failure to use them properly may damage the mouth of the horse. Once the mouth is damaged, the horse will find it hard to respond at once to the commands and directions of its rider. Wrong usage of curb bits can also result to unbearable pain which causes horse's disobedience and radical behavior. The worst scenario that might occur is a fall-off, fatal accidents and other casualties.