Equipment: small plastic container; needle; cork; magnet; knife; permanent marker pens

Cut a slice of cork to about 5mm thick

Magnetise the needle by stroking it several times along the magnet from eye to point in the same direction.

Push the needle carefully through the cork across the circle.

Fill the container with water and float the cork in it.

Check with a compass which end of the needle points to North and mark it on the cork.

Fill in the other compass points.