This is a fun paper-folding activity that we did at the 2015 Karate Summer Camp.
Start with a rectangular piece of paper. We used paper bags (like you would get at the card shop; not grocery bags, which would be too heavy).
Fold the bag in half, lengthwise, then open it back up. Using the crease as a guide, fold in the two corners at one end to the center line.
Repeat this on the other end, then fold the whole thing in half, with the flaps on the inside. (Fold the bottom half up.)
Fold your shape in half, then open it back up again. We will use the crease as a guide.
Now fold one side up, so that the bottom edge follows the crease we just made. Repeat on the other side.
Turn your shape over, and fold it in half so that only the large triangles are showing. (The smaller layers are on the inside.
To snap it, grasp it by the tips of the large triangles (at the top of the last picture), and snap it downwards.