A method and a system for forming slider end stops on a zipper tape that comprises first and second interlockable zipper parts. The method comprises the following steps: (a) transmitting sufficient ultrasonic wave energy into first and second areas of the zipper tape to cause the first and second interlocked zipper parts to deform and fuse in the first and second areas, the first and second areas being separated by a gap; and (b) applying sufficient heat and pressure onto a third area of the zipper tape to cause the interlocked zipper parts to deform and fuse in the third area, at least part of the third area being located between the first and second areas in the gap. The first and second areas do not impinge upon the zipper rails. The third area does impinge upon the zipper rails. Thus the zipper rails are deformed in the third area, but not in adjacent areas located below and contiguous with the first and second areas. The zipper tape and packaging film are cut along a midline of the third area to sever each package from the continuous web.