http://www.youtube.com/watch?v=qdRit8Vr8FM&feature=youtu.be (Kinda starts suddenly but it starts with the little button being pressed on the top left of the part) This pencil case has secret departments. The key pencil topper opens up the ruler compartment and the ruler opens up a separate compartment to store erasers, lead, paper clips, etc. There is a spring (like the one that holds the side compartment in) that pushes the top of the pencil case up as the button is pressed. Everything on this pencil case is printable. There are no external parts required. I wanted to have a printed prototype but I haven't had time to print it. It isn't perfect but I did print out the spring parts and pivots parts to ensure that everything works as intended. It's kind of complex so I uploaded a video to show how it works. If you have any questions let me know. This is my first upload on thingiverse so feedback is much appreciated! Thanks for checking in :).