The upright steel plate in a flintlock gun which is struck by the flint in order to produce the sparks for igniting the priming powder. Note: the sparks come from the steel NOT the flint

The frizzen is a curved plate of steel used in flintlock firearms. When the trigger is pulled, the hammer, which includes a shaped piece of flint held into a set of jaws by a scrap of leather, snaps forward causing the flint to hit the frizzen. This in turn causes a shower of sparks to be thrown into the pan, which contains black powder, this ignites and sets fire to the powder in the touch hole.