It happens to even the best-equipped cooks--whether you're in a friend's kitchen, or in a vacation rental house, you find yourself stuck with a horribly dull knife, and no sharpening stone or honing steel at hand.
Turns out there's probably something in the cabinet that'll work in a pinch--the unglazed bottom rim of a ceramic coffee mug. Just place your knife blade at a 20-degree angle to the ceramic edge, and draw it from heel to point several times on one side of the blade. Then turn the knife over, again at a 20-degree angle, and repeat on the other side. You'll find the ceramic surface does a surprisingly good job of sharpening the knife.
See more knife skills videos.