First, build a strong base out of small pieces of wood and some screws or nails. A thin rod anchored to the base serves as the axle. Drill a hole through the arm of the catapult, and run the axle through it, making sure the movement of the arm is unimpaired. Use rubber bands or bungee cords to provide the elastic tension needed to pull the arm of the catapult down, and attach a basket to hold the projectile.
Catapults are common school projects associated with either physics or history classes. A typical physics catapult project has specific requirements regarding the performance of the catapult or its construction style. Catapults made for history classes tend to have requirements regarding the appearance and historical accuracy.
All catapults consist of some sort of base, a basket in which the projectile is placed and something that provides the elastic force used to launch the projectile. Catapults come in all shapes and sizes and range from simple to complex. A marshmallow catapult, for example, can be constructed out of Popsicle sticks, rubber bands and a plastic spoon. A tabletop catapult can be built out of small pieces of wood, a few screws or nails, and rubber bands.