Movements
Rein-back
A rein-back is a movement in which the horse steps backwards with the legs moving in diagonal pairs. It's feet should be lifted well off the ground and not dragged.
The first 25 seconds of this video show a horse at the walk that halts and then completes the rein-back.
Schaukel
A rein-back schaukel is an advanced move. It is performed when the horse walks back a set number of steps, then immediately forward for several steps and then back again for another fixed number of steps. The legs should step back in diagonal pairs and should never be set down parallel to each other. Proper performance requires the movement to be fluid and straight without hesitation from the horse. It is a difficult move to perform and measures a horse’s obedience.