The rocking horse is a variation of the rider-on-top/cowgirl position. Instead of laying on their back, however, the penetrating partner starts by sitting cross-legged and leans back, supporting themself with their arms. The receiver then kneels and straddles them.
More About The Rocking Horse Position
This position gets its name from the rocking motion the receiver must do to facilitate thrusting. For additional stability, the giver can also lean against a solid object, such as a headboard or wall. This position also makes it easier to stimulate aclitoris, either manually or with a clitoral vibrator.