Our group adapted the repeatable module we developed for our equilibrium model to construct six umbrella structures for the reciprocal model exercise. The plank itself was extended by half an inch on each edge to accommodate a new system of grooves. To allow for a greater variety of combinations, slots were added to the center of some of the pieces. The addition of the grooves and slots, elements that act in compression, helped us stabilize our six umbrella models, which were much larger and more complex than our original equilibrium models. Once again, cotton twine was used to provide tension.