Sharpening a knife is a skill that everyone who enjoys cooking needs to have. I have several stones for sharpening my knives. In addition to having the correct stones one of the most difficult things is to maintain the angle between the knife and the stone during the sharpening process. There are many videos and even YouTube channels on the subject. A video that caught my attention is below. It shows how to create and use an electronic device to maintain the sharpness angle.