Abstract: A stackable modular cabinet having modular, interlocking side units which allow cabinet dimensions to be tailored both vertically and laterally to user needs while also providing the strength and stability to support heavy equipment such as electronic subassemblies. Each side unit has a pair of mating flanges with apertures for receiving and retaining fastening pins that interlock to the fastening pins of a different side unit when the respective flanges of the two side units mate. The interlocked fastening pin structure forms unified rods which extend the full height of the cabinet and which cooperates with the intervening side unit flanges. Each side unit further has re-enforced, double-sided bracket structures at opposing ends which, in combination with the pin structure, provides an unusual amount of strength to the modular cabinet.