When the characters are engaging in a Bavarian Fire Drill, are Impersonating an Officer, need to infiltrate the enemy base, or are Dressing as the Enemy, their credibility is greatly enhanced if one of them is holding a clipboard. Nothing terrifies human beings as much as an Obstructive Bureaucrat on the move.
See also Refuge in Audacity. This is of course Truth in Television, as shows like The [...] [tvtropes.org]