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.

First, six squares joined in a cross fold up into a cube.

Now six rectangles fold into a cuboid, with opposite faces matching.

This next one is a different shape, but it still folds into a cube.

Here is a triangular prism folding up. Notice the two triangle ends and the three rectangles between them.

This last arrangement has six squares too, packed in a block. Before it folds, decide whether you think it will close into a cube.

Now we build our own nets together on the front board and fold them to test. Pupils take turns coming up to place the squares, and everyone else predicts out loud before each one folds.

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