A paper popper is a party prank that is commonly used in schools. There are many variations of a paper popper, but they all involve a folded sheet of paper being gripped and right down. This causes air to be forced into the paper's holes, making the paper flaps pop out in the opposite direction, then making a loud popping noise. According to popular misconception, the sound is supposed to be caused by the paper breaking the sound barrier. In actuality, what happens is that air rushes in a blast wave to fill the vacuum created in the pocket that opens. The sound is described as the crack of a whip, which is an example of breaking the sound barrier, although the causes are different. Most papers work for poppers, although some are louder and some are quieter than others. Using bigger paper makes it louder and book paper also makes it louder.
Rectangle paper popper:
First, fold the top/bottom of the paper down to the bottom/top holding it landscape.
Second, still holding it landscape, take the right/left side and fold it in half
It is now done. To use it, take the 2 outer pieces of paper and move them down while holding onto the 2 middle pieces of paper.
And then, like every other paper popper, hold it high and then move it quickly downward.
To reset it after using it, unfold it, since it should be folded in half to redo the previous folds.