Secret Locking Box!

A fun brainteaser that will be sure to leave people stumped! I modeled this after a puzzle box my aunt gave me as a child. Once I finally figured it out, it blew my mind.

Assembly

Superglue is highly recommended in order to ensure the pieces don't come loose when the box is in the locked configuration!

Step 1: The Box

Insert 5 pins into the piece with the yellow arrow into holes 1,3,5,7 and 9. Ensure the hole are oriented so that they are closer to the top as this piece is not symmetrical. Then slide the piece onto the rails (black arrows) with the weighted end of the pins facing the outside edge of the box. I highly recommend a small bit of superglue on the rails to ensure this doesn't ever come loose.

Step 2: The Lid

Insert 4 pins into the piece marked with the white arrow into hole number 2,4,6 and 8. Then add some glue to the piece and lock it into place in the lid ensuring that the pins have the weighted end oriented towards the outside edge of the lid. (It is designed with holes to lock into place like a block)

Next, insert the blank piece (marked with blue arrow) into the indentation under the pins. Add some glue to the pin coming out of the knob and flip the lid assembly while holding the blank (blue arrow) piece in and push the knob into that blank piece from the other side and allow glue to cure for a few minutes.

Next, insert the slotted piece (marked with a red arrow and complete the same process you did with the other knob to glue the knob into place with the slotted piece from the other side of the lid and allow the glue to cure.

How To Close The Box

Ensure all of the pins look as they appear in the picture below and ensure the slotted knob marked with the blue arrow is running paralel to the pins. Then just close the box and give it a shake back and forth.

That's it! Enjoy!

Note: The original print profile for this model included a duplicate part instead of the necessary part for the lid. I have updated it to include the proper part.