Look at the flat piece of cardboard on the screen. It used to be a box, but someone has opened it out completely and laid it flat.

What solid do you think it folds back up into? What clues are you using to decide?

Watch each flat net fold up. The colours show which flat shape becomes which face of the solid.

In the first one, keep your eye on a single square and see where it ends up.

In this one, watch which faces end up matching each other.

This next one looks different from the first, so watch whether it still closes up into the same solid.

Count the shapes in this one before it moves, and notice which ones end up facing each other.

Before this last one folds, decide whether you think it will close up or not, and be ready to say why.

Now we build our own nets on the front board and fold them to test. You will get a turn at the grid, and while someone else is placing squares your job is to predict.

We'll try these in turn:

• a cross of six squares
• a staircase of six squares
• a straight line of six squares
• a 2×3 block

Take a printed net, cut it out, fold it along the lines and tape it into a solid.

Once yours holds together, try the stretch: sketch a second net, a different shape from your first, that still folds into the same cube. To find one, try moving one square to a different edge, then predict before you check whether it would fold.