Whether you use it to clean fish or to set up a campsite, keeping a field knife sharp can be a tough job. Although there are many options for sharpening a knife, such as whetstones or carbide sharpeners, there are several other low-tech techniques. Any smooth stone can be used to give a knife an edge, including an average red brick. Bricks are made of ceramic, which is also used to make many different kinds of sharpening devices.
Smooth one side of a brick by rubbing it on a concrete or cement walkway for 30 seconds to 1 minute. This will remove any rough spots on the brick and provide a smooth surface for which to sharpen your knife.
Hold the side of the knife blade parallel and flat on the smooth side of the brick, and adjust the angle depending on the amount of bevel you want on the blade.
Slowly push the blade across the smooth side of the brick away from yourself. Start with the base of the knife and repeat the process continually moving toward the tip.
Turn the knife over and repeat Step 3 on the other side.
Test the knife's sharpness when finished by slicing a piece of paper. If it cuts through smoothly, the knife is sufficiently sharpened.
The angle at which you sharpen your knife will depend on what you will use the knife for. A 25 to 30 degree angle is good for hunting or field knives, as it provides a strong and durable edge. For kitchen cutlery, use a 20 degree angle. Anything below 18 to 20 degrees is usually reserved for razor blades or scalpels. This provides a very sharp edge, though it also makes the blade very delicate.
Be careful not to cut yourself when sharpening a knife. Always sharpen by pushing the blade away from your body, never pull it toward you.