In my wallet, I carry a fine grade with the strop on the back. I don't carry a two sided plate because I try never to let my knife get so dull that I need the medium grit. Besides, I've already got it. Stones Stones are the more traditional way to sharpen knives. There are many different kinds, but they can be roughly divided into Western and Japanese styles, both of which come in natural and artificial varieties.
Stones are much softer than diamonds, and wear away in use.
The residue tends to clog the surface and interfere with the cutting action. Japanese stones avoid this by wearing away quickly, and exposing a new surface. They are used with a lot of water to flush away the residue, and require a lot maintenance to keep the surface flat. Western stones wear more slowly, but still require liquid to flush the residue away. They also wear away to some extent, and require occasional flattening.