The rack comprises a plurality of hollow, sheet metal shelves supported in spaced, horizontal planes by four tubular corner posts. Two rows of animal cages of generally box-like configuration are removably suspended beneath each shelf, with the upper, open end of each cage disposed in near sealing engagement...http://www.google.com/patents/US4249482?utm_source=gb-gplus-sharePatent US4249482 - Air conditioned laboratory rack for animal cages
