I once saw a Gospel tract that was made out of thin cardboard that you could fold over and over forever and it would just turn itself inside out. Here is a 3D printed version of that idea. This is my first version, so I am sure to improve it. Video of this thing in action: https://www.youtube.com/watch?v=6-CDlkO9rjQ You can make this a few different ways. If you are daring, you can print Section1of2 and Section2of2, remove the supports and snap them together. Or, you can print all the pieces separately and snap them all together. if you do the later, you will need to print 2 of each of the following: L-left, L-right, Panel-long, Panel-short. you will need 4 of the following: Hinge-long, Hinge-short. I also included an stl. of the complete assembled model. I doubt oyu could print this with a single extruder as you cannot orient the model without either the panels welding together or some of the hinges falling apartt. I am working on another version that can be printed as one piece. i think i know how to do it, I just have to spend the time on it.