Electric diamond knife sharpener The battery-powered diamond knife sharpener is perfect for Kyocera ceramic knives. Care and use: Hold the knife sharpener in your left hand. Press the ‘Run’ button while introducing the knife blade to the sharpening slot. Begin with the wide part of the knife and slowly draw it through the slot with several movements to achieve a noticeable level of sharpness. Repeat this process in the other slot to alternately sharpen the slides of the blade. You will need four AA alkaline batteries which are not included in the scope of delivery. The whetstone cannot be replaced. It removes defects up to 0.5 mm deep in the knife blade.