Cut two, 1-inch diameter PVC pipes so they are 4 inches longer than your hoop house, using a pipe cutter or hand saw. One pipe is needed for each side of the hoop house.
Drill a small hole through each end of the two pipes, placing the holes 1 inch in from the end of the pipes. Drill a hole through the top cross bar of the hoop house at either end of the bar.
Cover your hoop house with the 6-mm thick plastic sheeting. Roll the end of the plastic around the prepared PVC pipe on each side, securing the plastic to the pipe with silicone adhesive. These pipes are the rollers, which sit on the ground when the house is closed and raise up when the plastic curtains are raised.
Run a nylon cord through the hole in the crossbar and down through the hole in the corresponding end of the roller pipe. Knot the ends of the cords so they don't slip from the holes. Repeat for each end of the hoop house, attaching a cord through both ends of the two roller pipes.
Raise the plastic curtains by pulling up on the nylon cord where it protrudes from the top crossbar. Clip the cord to the top crossbar with a clamp so the curtain doesn't fall back down. Close the hoop house by removing the clamp and allowing the roller pipe to drop back to the ground.