Abstract: 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.