This flash guard can be used on a Brown Bess ,Charleville, or French Fusil musket. The guard is installed on the lock by removing the frizzen screw and then put the screw threw the guard and screwed back in the frizzen. Depending on what lock you have, the guard has a ear that is on the back side that will rest on the lock so that it will not swivel. If this ear interferes with the lock the ear can be filed or ground off.