Hardware for Panels and Rolls, H-Channel and Clips Flexible, snug fitting PVC H-Channel slides between Solexx seams for a flush finish and tight seal. Clips are used to join 4′ H channel pieces together for horizontal installations. U-Trim and Caulking, U-Time PVC edging caps off open flutes of the panels. We recommend you first run about ¼ inch of silicone caulking into the open edges of the panels to seal out bugs, dirt and moisture The trapped air from the caulking helps achieve the highest possible insulation. Solexx Sealing Screws, White galvanized screws with ¼” hex heads secure the greenhouse covering to the frame of the greenhouse. No pilot hole required! Soft neoprene washers seal out moisture. Use 1″ screws for wood or PVC frames and 1″ self-drilling screws for metal frames. Screws are sold in packages of 100.