Step 1
Cut a trapezoid shape on each of the large sides of the box and cover it with brown paper, or paint it, or just leave it as it is.
Step 2
Pierce two holes at the top of the sides of the box. Insert a skewer through these holes and then take the skewer out. Trim a second skewer to 9" (23cm), to form the PIVOT and lay it at right angles to the first skewer.
Step 3
Tie the skewers together with string, keeping the right angle. A dab of glue can be useful to keep it in place.
Step 4
Using sellotape, fasten the scoop to the pointed end of the long skewer. It can help to push the point of the skewer through the base of the scoop, but it is not necessary. Sellotape the pebble firmly to the other end of the skewer. This is the COUNTERWEIGHT which causes the long arm to swing up and launch the missile!
Step 5
Ease the PIVOT through the holes in the side of the box, and allow the counterweight to swing freely.