George Miller's "Three Card Burr"
Three cards interlocked along three axes to form three intersecting planes. Assembly requires that the cards are bent and stressed quite a lot. Once assembled, the cards "lock" into place and disassembly is a next to impossible task.
Inspired by George Miller's "Three Card Burr".
Here's a PDF template that should print the card outline at the proper size. (Make sure scaling is 100% when printing.)
I cut all my cards at the same time using a scroll saw. I taped the 30 cards together into a packet and affixed the template on top before cutting through all the layers at once. Much easier than cutting each one by hand with scissors.
It's a puzzle and there are only three pieces. Figure it out!