Cutting with a dull knife only wastes time in the kitchen. Sharpening your knives regularly allows you to get more precise cuts, making it easier to cook your food quickly and evenly, and sharp knives are less prone to slipping, saving you a trip to the emergency room. However, if you do not own a knife sharpener, you can use a ceramic mug. Turn the ceramic mug upside down and slide the knife across the bottom to sharpen it since the bottom it is unglazed and rough.