Sewing plastic sheeting together may seem like a daunting task but can actually be as simple as sewing any other fabric together. The key to sewing plastic sheeting is to keep it from ripping and weakening the area around the stitches. As long as you keep it securely pinned or stapled together, it should sew together easily. Sewing plastic together is actually a better option than trying to tape or glue it together, as the sewn knots are closer together and less damaging to the plastic.
Pin the plastic sheeting together using standard sewing pins at 3- to 5-inch intervals. If the plastic sheeting is very thick, you can use staples about 6 inches apart.
Select a sewing needle that is used for denim, leather or other thick fabrics if sewing by hand. If you are sewing together a plastic sheet that is thin, such as a plastic grocery store bag, a standard-sized needle and thread will work, like one you would use for sewing cotton.
Use a stronger thread, about size 69, which is used for leather work, to hold together thick plastic sheeting. You shouldn't need waxed thread to help you get through the sheeting as you would through leather.
Sew the sheets together as you would fabric. Follow the instructions for your project or simply overlap the pieces and sew together as needed. Don't pull too tightly, though, or the sheeting will pucker.
Use a sewing machine with a needle and thread suitable for denim or fleece materials. A sewing machine will be difficult to use, though, if your sheeting is very large.