These sharpening stones are made from a synthetic abrasive material and are used in the same manner as a diamond or natural bench stone. The extra-coarse side of the stone (100 grit) is used for aggressive removal of metal and will sharpen a dull or damaged blade very quickly. The other side of the stone (240 grit) is for less aggressive removal of metal and should be used for sharpening somewhat dull blades that just need a quick touch-up or for smoothing the cutting edge after sharpening on the extra-coarse side. It is excellent for use on pocket knives, sport knives, tactical knives, or other cutting tools. Instructions: Rinse your stones under running water and dry after each use. Occasionally, you should clean the pores of your stones by vigorously brushing the surface with soap and water using a stiff, nylon brush. Store in a safe place, so that the stone doesn’t get broken.