curb chain

plural curb chains

1. equestrianismA chain running under the chin and attached to a curb bit, used to prevent the bit from rotating too much while limiting pressure on the upper palate of the horse's mouth.

   [H]ere and there curb chains, polished till they shone like silver, kept company with spurs, bits, stirrups, and other possessions, such as his saddle, a supply of spare girths, and a stock of horse medicines.

   1887, Harriet W. Daly, Digging, Squatting, and Pioneering Life in the Northern Territory of South Australia, page 86