Abstract: A modular assembly system comprising a plurality of structural members. Each of the structural members has at least one slot along a lengthwise side of the member. Each of the structural members is also defined by a unique spaced relationship between the predetermined slot-to-side distance and the slot-to-slot distance. The slot-to-slot distance is a whole-number multiple of the predetermined slot-to-side distance. Each of the at least one along a lengthwise side of each of the plurality of structural members is adapted to be detachably and selectively connected slot-to-slot to one of all of the slots along one of the lengthwise sides of each of the other structural members. In the preferred embodiments, the system also includes a circular support structure and an arcuate support structure.