Today I offer you an improvised knife sharpening tip. Improvised means it is not as good as a normal method of using a whetstone or other sharpener, but that it will work in a pinch.
If you take a ceramic coffee mug or bowl and flip it upside down you will notice a ring where there is no glaze.
It is possible to use this ring to sharpen your knife blade just as you would use a ceramic sharpening rod.
I have tried this, and it does leave residue on the ceramic ring, and it does sharpen the blade.
I would not use this for one of my high quality knives, but when out camping and I have to sharpen my knife “Right Now”, then this is a good idea to keep in the back of your mind.
The ability to break down a need into its component parts and see resources by potential function will allow you to always be able to improvise. Since the unglazed bottom ring of the mug can slowly act as sandpaper to wear metal it works to sharpen a knife.
Again improvised solutions are rarely efficient, but they do work in a pinch.
Hopefully this can help you in the future. If you have time, a purpose made knife sharpener does work much better.