Abstract: An apparatus and method for producing a plurality of substantially dimensionally identical concrete structural modules. The apparatus facilitates the manufacture of a plurality of low cost molds of high dimensional accuracy which will consequently produce modules of high accuracy which can be interchanged, turned, and either horizontally or vertically assembled. A master pattern of the module having non-porous interior and exterior surfaces is positioned between inner and outer forms, the inner and outer spaces thus created are filled with a cementitious substance forming a mold having inner and outer mold segments with their mold faces formed against the non-porous pattern. The concrete molds are provided with various assembly mechanisms and shipped in matched sets to producers for use as forms in the production of the structural modules.