Polythene zipper doors are incredibly useful and versatile items when used with plastic sheet coverings and wraps. Zipper doors, or roll up doors as they are sometimes referred to are used mainly in the marine, construction and containment industries to create access for moving materials, equipment and people into a sealed area. Using a roll up door means that a cover does not have to be removed and re-secured to gain access to the product underneath. Using a zipped access door means that complicated doorways and ugly duct tape seal ups are a thing of the past. There are two main types of zipper door on the market.