Riding the horse
From wipipedia.org

Riding the horse refers to a method of punishment for a malesub. The "Horse" is similar to a sawhorse but with a pointed (but not sharp) beam. The male is made to stand with his genitals resting on the beam which is too high for his feet to be flat on the ground. Time becomes the enemy because eventually his legs tire and he must shift. This can provide an incentive to develop endurance in the calf and leg muscles in a graceful way since a loss of strength or of balance results in pain.