in a method for forming reclosable packages on a conventional form - fill - and - seal machine , a &# 34 ; y - type &# 34 ; zipper strip is fed toward and longitudinally down the filling spout thereof . a thermoplastic film is wrapped around the filling spout enclosing the zipper strip , and the lateral edges of the film are bonded together to form a longitudinal seam . the zipper strip webs are attached by sealing bars to the inside of the tube so formed from the thermoplastic film between the fill tube and the sealing bars . at intervals , transverse seams are formed to produce individual reclosable packages , which may also be separated from one another . the packages are filled with product during the course of their manufacture .