Answer: martingales

AnswerCrossword Clue
MARTINGALESStraps to prevent horses from rearing.
martingalesA gambling system of continually doubling the stakes in the hope of an eventual win that must yield a net profit
martingalesMARTINGALE, a strap from the reins to the girth of a horse preventing it from carrying its head too high also MARTINGAL
martingalesA strap, or set of straps, attached at one end to the noseband (standing martingale) or reins (running martingale) of a horse and at the other end to the girth. It is used to prevent the horse from raising its head too high