Breastplates or martingales are horse equipment that can be used together or separately. Breastplates keep the saddle from slipping back while you are riding. Martingales will keep the horse from tossing its head. Breastplates and martingales can come in a variety of leather types. These include flat leather, plain raised, fancy stitched or braided. Breastplates and martingales are normally made of leather. They can also be made of biothane or nylon.