Trot to tolt - ask the hindquarters to move over a little - and she stepped right into the tolt.
Functionally, why does this work? What effect does it have on the position of the horse's body and why does that cause him to move into tolt? I'm not being argumentative. I just do better when I understand the body mechanics involved. For Hunter, strongly gaited TWH, I just check him from any other gait and he immediately racks. He and Twist (Standardbred) both seem to have learned that when I sit from posting, they change gaits. Nancy