Actually I know what this is and part of how to use it. That part is pretty much a no brainer. What I have not figured out is how to use the brass bar to set the correct angle with. It says on it "Correct honing angle 30*" and at the very end of the tang it says 25. Does anyone know how you use this bar to set the angle with? I got a pair of them off ebay and the seller was no help at all.