Stand about six inches from side of box. Raise the foot closest to the box and place it on top of the box. Push off the box through your heels, changing feet in mid-air, such that you land on the opposite side of the bench with your other foot now on top and your landing leg slightly bent. You should have enough power that there is point in "mid-air" when neither foot is on the box. Continue alternating sides until you have performed all reps.