Bridging Shims for Swayback – If your saddle is bridging, you are missing contact in the middle of the horse’s back and there is too much contact at both the wither and the cantle. When using bridging shims, we recommend you start slowly. Use only one or two at a time. You will discover your horse will begin to lift their top line and develop more muscle with ThinLine. Once the muscle is developed it is often possible to remove one or all of the shims. Good news: you keep your ThinLine pad and horses continue to use their backs correctly.