From a dense paper size 5x5 cm make the dial, as shown in the figure. On the dial arrow with two opposite sides are located relative to each other at an angle of 90°. If the arrow on the right is 3 hours. At this time on the other side of the dial arrow is pointing up. If you rotate it vertically, the other party will be 6 hours. After that, the dial is rotated horizontally to the back side. Will be 9 hours. Arrow looks to the left. So after 9 hours was 12, turn the dial vertically and show the reverse side.