Abstract: The several embodiments illustrated in the FIGS. show welding apparatus for joining a plurality of plies of laminar thermoplastic materials held in and by gripping apparatus such as clamp jaws or belts. The weld is made by locally melting said plies by heating their protruding edges to a determined degree and for a determined period of time. Heat is brought into close proximity to the melt area and the gripping means provides a cooling means for the gripped plies of film. The completed welds are then cooled. The welding apparatus may be applied to material plies to seal their edges, or to seal the plies intermediate their edges. The welding is also shown as produced by continuous means and a heated ribbon may provide the severing means.