Three walls of freedom

Back in second grade, one of the fads was "Trapper Keeper forts".

You took your Trapper Keeper (and woe unto those who did not have an authentic Trapper Keeper), opened it wide, and stood it up so it formed a wall between you and the person facing you. You could then take one of the enclosed folders and spread it on top, thereby creating a wall for your fort. This was an effective way to ignore the teacher and cause mischief.

Sadly, now that I'm out of school, I work in a life-sized version of a Trapper Keeper fort. It's definitely not as much fun.