Naniwa knife sharpening guide (Degree adjustment)

Naniwa are renowned for their sharpening equipment, from professional whetstones used allover the world to little helpful gadgets like this. 

Using instruction:
1.Fix angle to the appropriate knife blade over the spine of the blade

2.Hold the handle and the back of the knife with both hands, the ceramic part must contact the surface of the whetstone or diamond. Hold the knife blade at a fixed angle, move the blade back and forth over the stone using light pressure.