Excellent tool for edge geometry training
I have always sharpened my knives by guessing and testing the blade, this tool helped me get them that bit better, its perfect for getting the angle right then using your thumb resting on the back of the knife and stone to help lock the angle as the bubble will sometimes play football and make a jelly blush with its wobbling around if you alter your angle or move to quickly, a well made little tool thats well worth its money.