Write the numbers 1 to 12 evenly on the back of the plate. Drill a hole in the middle and draw a pencil. Fix it on the bottom with a piece of plasticine. Place the watch made in this way in a sunny place. Rotate it so that the shadow cast by the pencil shows the current time.

Try drawing at different times of day and experiment with the angle of the sun and the shadows it creates as you track its journey across the sky. You can draw right on the sidewalk with chalk, too.