These zippers come separate from your netting and require sewing into position.
The installation method is to erect your netting enclosure, visualise the exact positioning of the zipper and then sew it in using the supplied twine. Once you're happy with the location and installation of the zipper, the netting is cut directly behind the zipper to create the opening.
DIY Zippers are available:
Vertical Zipper Kit (included 2m Zip, Twine and Needle)