While they aren't necessary for the sharpening process they sure make the experience a whole lot more enjoyable. This stone holder gets the whetstone you're using to sharpen your knives up off the surface you're working on giving you much more space for you knuckles. The rubber feet are also quite sticky and keep your whetstone from sliding around on even the most slippery of surfaces. 

Made from heavy duty stainless steel and easily adjustable by using the screws to tighten against the whetstone and fits every stone.