In the military, US Marines specifically, what are the rules about wearing your cover (hat)? As far as I know, it's off when you're indoors and on when you're outdoors, but I was looking for more specifics for a play I'm staging. Here's the scene: a small, intimate party, outdoors but under a tent, and the US President is in attendance, as are several Marines as guests. Should they have their hats on or off?