Use the ZipWall Heavy Duty Zipper when your barrier will be up for a while, if there will be a lot of traffic in and out, or if the worksite will go below freezing.Each HDAZ2 package contains 2 self-adhesive Heavy Duty Zippers, and 1 ZipWall Zipper Knife.For personnel, use one zipper for a simple doorway or place 2 zippers side by side to create a wide roll-up doorway that makes it easy to move tools and building materials in and out of the worksite.To instal the Heavy Duty Zipper, unroll it and determine its placement.Be sure the pull is at the floor and that the end of the zipper is below where the plastic bends at the floor.Then, starting at the top, peel the backing off one side of the zipper and press it firmly onto the sheeting.Repeat with the other side of the zipper.When the zipper is in place open it to the top and then cut the opening with the ZipWall Zipper Knife.This special knife has two blades that cut a channel from the sheeting.This prevents the sheeting from jamming the zipper teeth.This knife comes with each box of Heavy Duty Zippers.ZipWall is a registered trademark of ZipWall LLC.