Tired flint = needs knap :-D
I made a funny!!!
The edge of the flint has gotten dull and needs resharpening.
BLATANT PLAGERISM:
http://fp.enter.net/~kirschbaum/muzzledixon.htm#Ignition"Flint knapping is a simple process of chipping back the beveled edge of the flint. Since the flint literally scrapes steel (sparks) from the frizzen, the beveled edge becomes dull and/or filled with steel. A flint may be knapped many times to extend its usage.
One never thinks of knapping the flint until the gun misfires; that is, the powder in the pan fails to flash. When this happens, you have the choice of either knapping the flint or changing it. Remember, the rifle is loaded and a spark from knapping could bounce into the touchhole and thus set off the charge. For a right-handed person with a right hand lock, hold the rifle so the left hand wraps around the lock in a position so that the index finger is placed against the touchhole. With the next two fingers, support the hammer, especially if it is on full-cock. On some locks, the hammer may go back for enough on half-cock to allow knapping in this position. With the back of the patch knife or a knapping hammer, lightly strike at a slight downward angle. This knapping process will break off very small pieces of flint and any small pieces of steel that were causing the flint to ride over the frizzen."
The position described above seemed a little strange so I tried to follow the instructions, I couldn't do it. I cradle the rifle in my left arm, support cock and flint with left index finger. I use my brass short starter and tap downward on the edge of the flint till I get a new straight sharp edge.