Abstract: A system of interconnectable modular frame components for construction toys, playground climbing equipment and the like is based upon tubular triangular leg elements joined at about fifty-four degrees, forty-four minutes and seventy degrees, thirty-two minutes, being thereby modularly stackable at specific useful orientations. Complete triangular wall elements are joined with other complete triangular wall elements, forming tetrahedral modules which are then combined with other such modules by transverse attachment of the tubular legs of each said module, the tubular legs being coextensive structural elements in structures built from attached modules.

Abstract: A modular educational erector-toy and erector playground equipment and building system for constructing single-level and multi-level toy and playground structures and buildings of widely variable optional combinations of hollow primary tetrahedron modules and secondary tetrahedron and hexahedron modules and tertiary pentahedron and septahedron modules; the modules being full-size, half-size and quarter-size. The modules are bounded by planar walls, with the outer surfaces on one or more walls of each module matching the whole or an integral fraction of the outer surfaces of one or more walls of every other module. Some or all of the walls of the modules have substantial openings or windows therein so as to form planar boundary flanges or webs defining such tetrahedrons, pentahedrons, hexahedrons and septahedrons.