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I made one of these in class yesterday while the kids were taking a test. Since it's a youtube video I had to do it from memory, and when I was done making it it didn't seem to want to fold right, so I thought I'd messed it up. I just set it to the side. Next block my scary bright student was, "Oooh what is that. Can I play with it?" followed by a "WOW" when it started flipping inside out. Turns out I wasn't forceful enough.

While hitting up the other teachers for a glue stick to glue the hexaflexagon together, one of our geometry teachers handed me a little article on how to make these:

http://www.georgehart.com/slide-togethers/slide-togethers.html

The hexaflexagon video? Vi Hart. The Slide Togethers? George Hart. Father-daughter team.

I very much suggest her video on sound:

http://www.khanacademy.org/math/vi-hart/v/what-is-up-with-noises---the-science-and-mathematics-of-sound--frequency--and-pitch