an access floor panel construction employing peripheral trim channel elements joined together at the panel corners and fixed at their mid - lengths to the edges of a main body . as disclosed , the trim elements are of an organic thermoplastic material and are ultrasonically welded together at their ends and thermoplastically deformed into receiving portions of the main body edges . an assembly fixture holds the trim elements in position for final assembly in a manner which reduces the size of any gaps which might occur as a result of dimensional tolerances in the panel components .