Side passing is a common skill frequently taught to horses by trainers after the horse has the basics of being ridden trained reliably. Side passing is a Western maneuver in which the horse moves laterally sideways without moving forward. Officially, the side pass is never done with English horses. English horses may be trained to half pass or leg yield, but both of these movements integrate foreword as well as sideways movement.
The cue for side passing a horse is usually pressure on the side you want the horse to move away from. To cue a horse to side pass, sit deep in the saddle and weight your seatbone on the side you want them to move away from. Apply pressure with that leg as well. By applying pressure and weight on one side of the horse and lifting the seat bone and leg on the other side of the horse, you create an open door for the horse to move into. A horse correctly trained to yield to pressure will side pass obediently away from the leg. This is the most common cue for asking a horse to side pass.