I've been exploring mechanical components you can make out of cardboard (see my cardboard spring), and I really like this one. I can't figure out what it's good for, or what this set of properties is called, but maybe you folks can help me out with that?
It's flat and rigid one way, or bendy if you flip it over. Like this:
Pretty cool, right?
All you have to do is score a strip of cardboard so that it goes through the top layer and the corrugation on one side, but leave the other side intact. Use a blade and a straightedge.
If you do a few perpendicular lines the long way (as shown), it performs better on the rigid side.
Please comment to let me know if you need more instruction to figure it out!
P.S. If you think of something cool to make using this (and it's still before 7/13/12), you should enter it in my Cardboard Challenge!