If man looks from the top of the grinder in the V-shaped inserts, notice that the knife last has left contact with the abrasive ceramic. Now it does not matter how you hold the knife, you end up on the ceramic side facing away from a ridge, which you can feel with your fingernail. One can indeed very very carefully edit again to the ceramic piece on top of the grinder, but really convincing, the result is not. I personally achieved with the use of one or two grinding stones and a lot of time much better results.
But you can quickly create a basic grinding it, but better the result, if you still refinishing with a fine example 6000 Arkansas stone. Then the result is okay.
Conclusion: Better than nothing, but not suitable as the sole abrasive tool.
