Sharpening hedge trimmers involves a few steps. First, you must clean the blades to remove any dirt or sap. Then, using a flat file, follow the angle of the cutting edge of each tooth, filing in one direction toward the sharp edge. After filing all the teeth, use a whetstone to hone the edges for a sharper finish. Always ensure you're wearing protective gloves and following proper safety procedures when handling and sharpening the blades.