The tool opens to show a square. You can draw lines of symmetry on this shape. If you get this right, your line becomes a black dashed line. You can then demonstrate folding the shape along this line by clicking the ‘Fold’ button. You can then click the ‘Unfold’ button to unfold the shape again.

If you draw a line somewhere other than on a line of symmetry, your line will flash before disappearing.

If you click ‘Show Lines’, the tool will show all the lines of symmetry for this shape.

To replace the square with another shape, click on a new shape from the selection on the left of the screen.

Clicking ‘Reset’ undoes any changes, returning the tool to its default state.