Abstract: Methods for forming a thermoplastic film with an attached closure strip are disclosed. The thermoplastic film can then be used to produce zippered reclosable plastic bags. The methods include providing a thermoplastic film web having a sealing surface and providing a closure strip having a binding surface, both being maintained in a non-melted condition at room temperature. A heated thermoplastic binder layer is then extruded and positioned between the sealing surface of the film web and the binding surface of the closure strip very quickly after extrusion. The hot freshly extruded binder layer transfers enough heat to the closure strip and to the film web to melt the binding surface of the closure strip and sealing surface of the film web. Pressure is then applied to the film web and the closure strip to seal the closure strip to the film web. An apparatus for practicing the method at high speed is also disclosed.