What shape do you get if you tear open a box and lay it out flat? A drawing that unfolds a solid shape's surface along its edges like this is called a net. A cube is wrapped in six identical squares, so its net is also made of six squares. But here's an interesting question — does gluing six squares together any which way always give you a cube?
The answer is no. There are hundreds of ways to join six squares edge to edge, but among all of them, exactly 11 arrangements actually fold up into a proper cube with no overlaps and no gaps. The most famous one is the plus-sign (+) shape, but surprisingly, some jagged, staircase-like arrangements also make the cut.
Why doesn't just any arrangement work? Fold it and the reason becomes clear. If all six squares are glued in a straight line, some faces end up overlapping when you fold it while other spots are left completely empty. A cube needs exactly six distinct faces, and an invalid net simply can't satisfy that condition. If it's hard to picture the folding in your head, actually cutting out paper and folding it is by far the surest way to check.
Nets matter for every solid shape, not just cubes. Designing a shipping box that uses as little cardboard as possible while still folding up sturdy is a real problem in industrial design. Even building a curved roof in architecture relies on a similar idea — figuring out how to cut and join flat material so it forms the curve you want.
When studying this with kids, the best approach is to actually cut out six squares from paper, try arranging them different ways, and fold them to check whether each one really makes a cube. After a few tries, you'll start to develop a feel for "this shape looks like it'll work, that one probably won't" — and that feel is exactly what spatial reasoning is. On our activity page, you can control a 3D viewer with a slider to watch a net actually fold up, compare all 11 correct arrangements against ones that don't work, and check your understanding with a quiz.