Abstract: Packages being produced on a form, fill and seal machine as provided with transverse zippers inserted thereinto through a fin seal gap. Pairs of fin sealing bars are separated by a gap to produce the fin seal gap. The fin seal gap is opened, perhaps by vacuum means, and a zipper probe inserts a zipper having a web into the tube of plastic sheet material being formed into bags. The web of the zipper is sealed to the plastic sheet material, and the zipper probe withdrawn from the tube. Cross seal jaws seal both transverse ends of the package, a knife separates each package from that previously made, and a fin gap sealer seals the fin seal gap to complete the manufacture.