Composite bombardment inhibiting section for frame members

A composite section for forming blast resistant panel frames comprising a base section, an intermediate section having a first side secured to said base section and an opposite side remote from said first side, a plurality of projections extending from said opposite side in a direction away from said base section said projections being integrally formed with said intermediate section, length wisely co-extensive therewith, and being elastically pivotable with respect thereto, said projections including nose portions directed laterally to one side of said projections, a rigid generally planar cover section of thickness in excess of the length of said projections and including grooves recessed into the body thereof and opening toward said intermediate section, said grooves being spaced to receive said projections, said grooves being defined by side walls, a bottom and a mouth facing said intermediate sections, said side walls flaring progressively outwardly in the direction of said mouth to define a cam configuration, said grooves being of substantially greater cross-sectional extent than said projections and including laterally off set enlargements adapted to receive said nose portions of said projections, said projections and grooves being arranged in pairs, said nose portions and grooves of each said pair being oriented in mirror symmetry.