How do you keep a head horse from shouldering into the steer?

A head horse that shoulders into the steer — drifting its body toward the steer and making contact or crowding it off its line — creates problems on multiple levels: it alters the steer's direction and speed unpredictably, it takes away the header's swing room, and it can result in a no-time if the horse's body interferes with the steer before the catch. The cause is almost always a horse that lacks lateral control through its shoulder, either because the training did not specifically address shoulder positioning at speed or because the horse has a natural tendency to drift toward the pressure of the steer. The correction requires that the horse understand and respond to the outside leg at speed — the right leg of the rider pushing the horse's shoulder away from the steer while still driving forward. This lateral responsiveness must be installed in flat work before it is asked in the roping pen: shoulder-out exercises, spiraling circles outward, and straight-line work where the rider uses one leg to move the horse's shoulder laterally without affecting the forward pace all build the response the horse needs. In the roping pen on slow cattle, practice running alongside the steer with deliberate use of the outside leg to hold the horse off the steer's body at the correct distance. Some horses shoulder in because the rider has inadvertently trained them to do so by using the inside rein to position the horse, which pulls the horse's nose away from the steer but lets the shoulder continue drifting in. The fix is leg, not rein — the outside leg holds the lane while the horse's body stays straight and parallel to the steer.