This is a great tool to help create consistently sharp edges. In theory, it's a scale with a calibrated test media which gives a readout in grams of force needed to sever the media. In reality it's like having a QA team in your shop to ensure edges are as sharp and as consistent as the maker thinks they are. I am sometimes surprised by a reading that shows higher than I would expect after a sharpening session, and I think this tool keeps me honest. A paper test is one thing, but this tool gives a much more exact reading as to the state of the edge. A spool of media goes a long way, but get an extra spool so you aren't caught in a bind, wishing you had just one more test.
