The double dovetail puzzle is a classical brain teaser that defy intuition at first... How the 2 pieces where assembled with these two dovetails? I've added a twist inside to raise the disassembly difficulty. You can see the puzzle in action in this video: https://www.youtube.com/watch?v=djktBAgd2qUThis is my first brain teaser (and most complex assembly so far). You need 2 marbles (1/2inches diameter, STL provided) for the internal mechanism. I've added a 1mm clearance in the marble slots and the dovetails. I finaly printed this one in PLA, 2 shells 20% infill, and got my first experience with warping on a non-heated bed... Only the external faces were warped, and the dovetail part was pretty flat, so I just had to do a little bit of sanding to make it slide nicely! When doing the right actions there is a maximum of 4 steps to open the puzzle, but there are traps and dead-ends that will play tricks with anyone who's tempting to solve it. It's not an difficult puzzle probably 3/5 but should be challenging enough. You can check the solution here: http://wp.me/p3gI7M-2M at the end of the post. To assemble the puzzle: 1/ push the 2 marbles in the holes (1 per piece) 2/ hold each marble/piece between the thumb and forefinger 3/ completly slide the the pieces starting with the corners with the arrows 4/ try to disassemble it!