So what exactly is a Hydro-Bat Hump Mold? The Hydro-Bat Hump Mold is a bat that you attach to your wheel-head and use while throwing. The mold attaches to the wheel with two rubber grommets embedded into the underside of the hydro-stone. After placing the hump mold on the wheel simply lay a slab on top of the hump mold. So think of it as throwing the backside of a form. You will still have to throw a foot by gathering clay from the slab or by attaching a coil and compressing it to the back. Hydro-Bat Hump molds allow beginners and professionals to consistently make forms with ease. We have a variety of forms and profiles within those forms. Just because these hump molds were designed to fit on the pottery wheel, doesn't mean you have to use them that way, they make great hand-building molds as well.