Some people think these are knife sharpeners.
They are actually called honing rods and keep knives sharper for longer.
The way it works is simple: let me demonstrate.
Pretend my hand’s are a knife blade.
As I cut, the knife blade is going to get more and more dull.
Slowly, the blade will start to bend out.
This is why you see chef’s using a honing rod while they cook.
It lets you keep the knife blade sharper for longer.
But you can only use a honing rod for so long.
Eventually you will have to sharpen to reset things.