My architect friends Lorenzo Bini and Roberta Pezzulla made this little project for a very young and dynamic client: Lorenzo’s 6-month-old goddaughter. They wanted to make a box that the child could use her whole life to store small, personal, precious things. So they created the UnaBox, taking inspiration from an Indian box (by an anonymous designer) that had an obscure opening system with 2 pivoting lids.

The box’s dimensions are based on the golden ratio, and it allows access only to patient and curious people; many adults have tried to open it and failed. Here’s how to build one yourself!

Project Steps

Cut the pieces.

The box is made from 11 pieces cut from a single board, plus a screw and a thin peg for the pivot and locking pin. Download a rough schematic, CAD drawing, and an assembly sequence at

To make the pieces, you can send the drawing to a CAD/CAM company and wait for the mailman, give it to a good carpenter, or cut the pieces yourself using a small handsaw or band saw.

Finish everything roughly with a wood file, and then more precisely with plenty of sandpaper.

Assemble the lid and box.

Following the plan, drill a hole in piece 11 and a slot in piece 9 that your screw will slide through (to cut the slot, drill each end and then thread in a saw blade). Also drill smaller holes in the pieces for the locking pin, running the drill only partway through piece 9. Drill both holes with the 2 pieces stacked together to make sure they align.

The diagram in the downloads section shows how the parts of the UnaBox fit together. With precise cutting, the bottom and sides of the box, parts 1­–5, should assemble with almost no glue; use small clamps to hold them while the glue cures.

Glue stacked pieces 6–8 together and glue them to piece 1, the bottom of the box. Also glue together pieces 9 and 10 for the box’s top. Once you’re done with the glue and the clamps, drill pieces 6–8 to hold the bottom of the pivot screw.

Finally, finish the box with a good natural wax and polish it. This makes the most of the wood, and gives it a nice smell and touch that kids love.

Learn the secret.

The closed box gives few clues to how it’s opened. You need to remove the peg and swing part of the top away before the rest of the top has enough clearance to slide back and swing open.

So far, we’ve built 2 of these boxes: the first one with olive wood, the second with cherry. If you build your own UnaBox, we would love to hear from you at


Get SketchUp and AutoCAD models of the UnaBox pieces, and drawings of the assembly sequence in Flash and SVG, at

This project first appeared in MAKE Volume 20, page 65.