Even a good knife will dull over time. Sharpening a knife can be easy if you have the right tools and know how to use them. The MIYABI pull-through knife sharpener has two sharpening modules with pre-set angles that make sharpening easy and safe. The first module restores the angle of the edge, while the second evens the edge to refine sharpness. ?Sharpens even the hardest blades to an acute 29? edge. Sharpens knives with a maximum 66? Rockwell Hardness.