Rectangular planar support members are slotted and interlocked to form vertical support structures. Elongated members slotted at each end are interlocked into the vertical support structure in horizontal and vertical orientations. The system is expansible in aligned or angled planes between vertical support structures spaced apart by the length of the elongated members. Components are easily assembled into myriad structures and disassembled to stack flat for storage. Each rectangular planar support member is slotted on four edges and provided with a tab on one edge. When the planar support members are interlocked together they form a column cross-shaped in cross-section and having slots extending in all four directions. The structural system therefore may be expanded in any of these directions by inserting elongated members in the slots and by adding columns as desired for multidirectional multiform structures.