If your knife isn't honed and you don't have a sharpener, you can easily make do by sharpening the blades on the bottom rim of a ceramic coffee mug.
Too many of us toss our knives in the dish washer, rarely sharpen them and continue hacking away at food as the edges of their expensive cutlery dull to near butter knife status.
If there's ever a time when a knife is too dull to work with, and you don't have a dedicated sharpener handy, all you need is a coffee mug.
Obviously, you will need a knife or two, so gather any you will be working with. You will also need a ceramic cup or bowl. Most ceramic dishes have an unglazed rim along the bottom. This is the most crucial part.
Just about any unglazed ceramic will do, but the larger the edge, the more room you will have to work with.
Keep in mind that this isn't exactly a standard way to sharpen a knife, and you probably shouldn't rely on it as a long-term method of sharpening. However, it will certainly do if you have no other sharpener on hand.
To sharpen a knife on a ceramic dish:
There should be some residue left on the bottom of the cup. This is a clear indicator that it's working and that it's shaving off extremely small bits of metal from the blade.
Continue this until the blade is sharp enough to use. Rinse the knife to remove any residual bits of loose metal and you're ready to go.