The de Gogue is based on the theory of three points of major resistance in the horse - the poll, the mouth and the base of the neck. The idea is that this aid overcomes stiffness in these areas and within the triangle created by the device, the horse learns to carry its head comfortably in the required lower position.
The De Gouge attaches to the girth, has a piece at the poll and goes through the bit and down to the girth again. The Beval Princeton De Gouge comes in Pony size with Havana Brown leather and brown rope. See larger picture