We've been invited to our squadron's annual ball in the officer's mess and the dress code is "black tie" which I think means "ball gown" for women. I've heard various instructions about length, covered/uncovered shoulders, whether the skirt can have a slit in it, ... but nothing consistent! Can anyone tell me what are the official rules, or where to find them? (I've tried 1358 but it just says "ball gown" without any more detail.)