Product details:

Usually only found in machine shops, the super flat face of the granite surface plate is ideal for leveling small plane beds, flattening waterstones and general sharpening duties. Simply soak a piece of wet/dry sandpaper in water and lay it down on the stone; the capillary action of the water adheres the paper to the stone, eliminating the need for spray adhesives or PSA sandpaper. When done, wipe clean with a paper towel. This A grade plate measures 12" x 18" x 3", weighs 80 lbs. and comes with a surface map. Plate does not have ledges.