This catapult fires using the same principals as a real catapult, except rubber bands replace rope for torsion. Once the arm is in an urpright position the hook can be inserted & the arm lowered via the winch. Once lowered the firing pin can be inserted to avoid misfire or the winch can be wound until the hook naturally slips off its catch, releasing the firing arm.
Range depends on torsion, but the less the better. To much torsion will smash the A-frame & send the skeletal hand flying across the room for added effect. Hey, at least you know it works!