And this folks is why I don't loan out my tools.i've built a few 1911s, can't say I really know what exactly the idiot mark is, or care enough to find out anymore than it has to do with the slide stop. The folks who do care probably also care about marring their AR lower while installing a bolt catch... if things like that matter to you, then by all means, take appropriate measures, if not, have at it with tooth and claw. It will work fine either way.