Abstract: The combination comprises a plurality of extrusions which are interconnected by means of a plurality of connectors thereby defining the modular system. The extrusions can also be interconnected end to end by means of joining members. The extrusions can be made of tubular members which have a first set of equally spaced radial projections provided with outer ribs to engage the connectors. There are also a second set of projections disposed between the first set of projections so as to enable panels to be disposed between the first and second projections. The connectors include a rod and clamping members at both ends of the rods to engage the ribs formed on the first set of projections. The joining members are spherical and have projecting stud members which are pressed fittingly engageable in the tubular extrusions for end to end connections thereof.