after you have removed internals including hammer, the flag can be removed easily, lift it out, and the lock is held in place by a tiny flat retaining plate that is the wishbone looking piece under spring tension (see the thing with the blue spring in original picture I posted), simply retract that and the lock falls out. You can install the plug and use this same retaining plate to hold it in place under spring tension, or use a tiny cotter pin that some of the plug makers ship with the plug to hold it in place and just dispense with the retainer plate and blue spring. I have done it both ways, both work.