The stirrups are shortened from the length used for flatwork, adjusted according to the height of the fence. Grand Prix jumpers and eventers on cross-country generally need to shorten the stirrups the most, to allow them to gallop and jump in motion with their horse. The short stirrup provides more leverage and flexibility, and therefore security, better balance and a more secure position should the horse stumble, get a poor distance, or peck on landing. More importantly, a shorter stirrup allows the rider to get off the horse's back between and over the fence, freeing up the back and allowing the horse to bascule. The stirrup leather should remain perpendicular to the ground. The stirrup iron is usually placed on the ball of the foot, allowing the rider to have a flexible, shock-absorbing ankle. The rider should keep even pressure across the foot, rather than pushing on the inside or outside of the stirrup iron, as this makes the lower leg stiff.