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Impossible dovetail box

3D model description

An impossible dovetail box with a secret locking mechanism.

A magnet and a 15mm rod are needed to complete this project. I used a 4mm wide by 3mm long round magnet and a 3mm*15mm rod, but a section of M3 screw will work too.

There's a F3D file so you can edit the size of the holes if you need to.

Press the magnet inside the "Top" piece, place the rod inside the "Bottom" piece.


The secret to opening this box is simple, there are two holes on each side of the box, the one on the bottom is deeper than the length of the rod, but the one on the top is half as deep. When the box is shaken or put upside down, the rod sticks to the magnet, locking both pieces together.

To open the box again, hit the box against a flat surface, the rod will fall back to the bottom hole, and the contents will be revealed.

How hard and how many times you have to hit it depends on the strength of the magnet. A neodymium magnet like mine will make it a challenge to open, adding a piece of felt on the magnet, beveling or rounding the extremes of the rod will make it easier. I found out applying a little pressure to the side will stop the rod from bouncing back and locking again.

3D printing settings

Material: PLA
Layer Height: 0.2mm
Nozzle: 0.4mm
Printer: Ender 3 Pro

  • 3D file format: F3D and STL



I'm a student and a maker. My passion is electronics.
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