Otherwise referred to as a martingale, the undercheck is designed for those horses who have a tendency to throw their heads up. When properly fitted, an undercheck will prevent the horse from getting his head higher than a normal position, rather than forcing him to carry it lower.

Similar in design to a regular Standing Martingale, this model includes a length of heavy elastic to allow some "give", while still maintaining downward pressure if the horse raises his head too high. This design is intended specifically for use with Buxton Breastplates. It clips to the centre ring of the breastplate at one end, and to the centre ring of the head halter at the other end.