The interlocking rolled-edge paperboard boxes for the prototypes were surprisingly simple to design and construct. I really didn't need any software. You can just measure them out with a ruler, cut, crease and fold them up. It's such a simple elegant design and works really well.
Start with a sheet of 0.45~0.65mm paperboard. What size depend on the dimensions of the box. Every millimeter of height takes 4mm of board width and height because the edges are folded over. You also need 10mm on all side for the wings that will lock together.
The KRED boxes needed to be about 50mm high, 280mm deep and 220mm wide. With a bit of trial and error, here's the recipe I came up with.
The Box
Start with 450mm by 600mm x 0.48 paper board.
Cut 92mm off of the height and 8mm off of the width.
Draw parallel lines in from each edge at 11mm, 61mm and 111mm.
Cut 11mm off of each corner leaving wings at the ends of each edge. The wings should be inset 2mm and cut at about 15°~20°.
[image: 2026-10-03 14.53.27.jpg]
The flaps should be cut with about 2mm gaps between them so the top and bottom walls will roll over them easily.
Use a glass cutter and a long ruler to score the wings on the outside face. Score everything else on the inside.
Fold and fit. That's it!
The Lid
Cut only 86mm off the height and nothing off the width. This allows the lid to be 3~4mm longer and wider than the box and it'll just slip over snugly.
Everything else is done exactly the same.
[image: 2026-10-03 15.00.20.jpg]
