If you have previously avoided sharpening household or outdoor knives yourself, now is the time to think again: The DUAL DIAMOND makes it really easy. Even delicate commercial knives can be sharpened with high precision.First, attach the vacuum suction cup foot on a smooth and stable surface. You now have both hands free and can run your knife along the grinding wheels.The two wheels - one for coarse and one for fine grinding - are coated with diamond powder. First you draw them through the coarse side and then through the fine side. The grinding angle is fixed - so it can go wrong. It‘s that simple