Strop a knife with cardboard and metal polish.

[@jeffreydavidconner]

If you look at a sharpened blade under a microscope before you do this. You will see burs and misaligned steel. After this process not so much. There are stones used to polish a Katana. But they are expensive. And if you don't know what your doing can damage your blade. This method anybody could do. I use it on my carry knives. I also have a old weightlifting leather belt that I use as a strop before the polish. When I am done you can shave with it. Nice video don't know how it got buried.