Portable underlying mattress stiffener

A portable mattress stiffener for forming a generally rectangular supplemental support panel assembly for bed mattresses adapted to be placed between a mattress and underlying box springs or the like, the panel assembly having a longitudinal axis to extend lengthwise of the mattress in use position and comprising a plurality of elongated rigid slat members of relatively thin, generally rectangular cross-sectional configuration each having a flat top wall and first and second side walls arranged in side-wall-abutting parallel relation in use position forming a rectangular panel, the slat members having longitudinal axes extending in parallelism transversely perpendicular to said longitudinal axis, hinge means interconnecting the respective slat members with each other at a lower edge of said side walls opposite an upper side wall edge adjoining said top wall and disposed at plural locations spaced longitudinally along said side walls of each of said slat members, the hinge means comprising interfitting first and second hinge formations, the first hinge formations being integrally formed along said first side and protruding beyond the face thereof defining an upwardly opening recess and the second hinge formations being provided at corresponding spaced locations along said lower side wall edge of the second side wall of each slat member and comprising a companion hinged formation interfitted in said recess defined by the first hinge formation, the interfitted hinge formations providing hinge axes at said lower edge of the said walls whereby the respective slat members are permitted to pivot about said hinge formation to arrange the slat members in a spiral roll disposition with the slat members angularly disposed relative to each other for transport, and said side walls of adjacent slat members forming abutment surfaces abutting each other when the assembly is unrolled to a flat use disposition to resist deformation of the slat members from a predetermined substantially uniform relationship with said hinge axes located adjacent the lower edges of the abutting side wall surfaces.