If you are schooling young horses, side reins are an essential training aid for any rider.
Side Reins for Horses
Side reins are clipped from the bit of the bridle to the surcingle or saddle and are typically used when lunging a horse. A common training tool, they are used to strengthen your horse’s frame and topline in order to support you safely. Once a horse has raised its back, collected its haunches and lowered its neck to ensure that it’s not feeling any strain, it will be strong enough for a rider.
Side reins encourage softness in the horse's mouth, provide a rein contact for a horse to work into, and depending on the positioning of the reins, can encourage various frames.