Haunches-In or Travers

The travers (haunches-in) is accomplished by the rider maintaining his weight in the middle of the horse, cueing with the outside leg back toward the flank, bringing the inside leg forward toward the girth to hold the forehand straight, and applying light direct rein of opposition to fix the bit so the horse does not bend his neck.
When viewing the travers from the rear, the observer should see the horse’s hindquarters move to the inside far enough to establish a perfect three-track. In moving to the left, the horse's left hind foot will track alone closest to the center of the circle. The right hind foot and the left forefoot track together, and the right forefoot tracks alone, farthest from the center of the circle.

Taken from the online course Training Performance Horses