1. Fold and unfold an A4 sheet of paper to make a centre line; fold the top corners down to the centre line to reach this diagram. Then fold the bottom corners up as shown.

2. Now fold the edge AB down to meet the point C in such a way that the point B comes to rest along the line BD.

3. The next thing to do is to fold the edge DE upwards to meet the line ACB. Ensure that all creases are sharp, because you will need them later. Now unfold the last two folds.

4. Fold and unfold the edges BD and AF similarly, the first down to C, the second to meet it. Now unfold all your good work except for the bottom corners.

5. Make a ridge (that's a fold in the opposite direction from the others) from corner to corner of the diamond shapes above the folded corners.

6. Now the tricky bit: nudge upwards at the last two folds to raise the sides of the box. Tuck the corners 1 and 2 into the box to hold all in place.

And there it is: an A4 piece of paper gives a 10.5cm square box. Smaller for computer discs, larger for CDs. (From a design by Professor Humi Huzita.)