What a rock! It is sized like folding an 8x11 sheet of abrasive paper in half -- one with perfect grit, flat, everlasting, and beautiful with the surface at just the right height. It's a serious razor hone smasher, and waterstone bout crusher. With a finger on your blade, you can apply a little moving pressure to make sure that even uneven blades are sharpened across the whole edge. Light mineral oil is a good lubricant for the cutting surface. It is odorless, has just the right viscosity to keep the swarf suspended, and makes it easy to see on this white surface. Some honing practice on this surface will give you a perfect edge, ready for polishing on a pasted strop.

If you buy another similar rock, you can rub the surfaces together, with silicon carbide grit between them, finishing two surfaces together, getting even flatter surfaces with great finish. Just sayin'.