Being able to put a keen edge on your knife is almost as important as carrying the knife in the first place. Since a dull knife won’t cut very much, every knife owner should have the skills to restore his blade to working order. Using the right sharpening equipment is an important facet of the operation, but once you have the right techniques down, you can literally sharpen your knife on a rock. Why do you think they call them sharpening stones, anyway? Here are three places you can sharpen your blade if you get caught without your usual sharpening equipment.