a zipper strip for a reclosable bag or package includes a male interlocking profile and a female interlocking profile . the male interlocking profile includes a male interlocking member and a male web coextruded therewith . in like manner , the female interlocking profile includes a female interlocking member and a female web . the male interlocking member snappingly engages into the female interlocking member to join the profiles to one another . one of the male and female webs is wider than the other in at least one of two directions from the male and female interlocking members , the greater width being represented by at least one flange extending widthwise beyond the other web . the zipper strip is designed to be attached to thermoplastic sheet material by sealing the at least one flange thereto without sealing the male and female webs to each other . methods for securing the zipper strip to thermoplastic sheet material , and for making packages on a horizontal form - fill - and - seal machine , are also disclosed .