Pieces
The catapult starts with two pieces of wood. Both are 3/4" thick. One is 3-1/2" wide and the other is 1-1/2" wide. Both are about 2' long.From these you cut six pieces. The pieces are the arm, stop block, pivot block, base and two sides.
You will also need some 3d or 4d nails (3d is pronounced "three penny".) And you will need a hammer, a saw and some glue. At the end of the project you will need a clothes pin, a rubber band and something to make wheels from.