Flints that have become dull and doesn’t produce sparks does not have to be thrown away. Here is a simple way to sharpen a dull flint. There are several methods of sharpening flints. You really don't have to use any special tools, but the first method I will describe requires that you modify a steel nail: Cut off the tip, and file a notch in the end of the nail, about 1 cm in length across half the nail. The tool is now ready. To sharpen a flint, place the nail against the edge of the flint in about a 30 degree angle (see the picture). The notch should be 90 degrees. Lightly tap the nail's head with a small hammer or similar. A small flake of the flint falls off and the 'wound' where the piece fell off will be sharp. Repeat this operation along the entire edge of the flint and it will be restored to normal again. Make sure that you use safety glasses because the flying pieces of flints are razor sharp.

A more simple method is to use a small brass hammer or the spine of a knife to sharpen the flint. This is my preferred method for sharpening flints. Tap the knife spine lightly on the top of the flint edge when the flint is secured in the jaws of the cock. Flakes will fall off and sharpen the flint.

Flints cannot be sharpened forever, and you eventually will have to replace it, but sharpening it by using the methods described above increases the service life of your flints.