Trimmed easily with fine toothed Sawzall blade to fit roof of harbor freight 10 x 12 greenhouse. Sealed with metal ducting tape on open ends. Took 12 panels total for full roof Used smaller 4mm panels for vents due to metal frame structure of vents nothing larger will fit properly in channels. These make harbor freight panels look like saran wrap in quality difference. After 5 yrs harbor freight panels yellowed badly and were flakey brittle showing hail damage. They also lost their insulating value last year or two. Waiting to see how long they last in Texas sun. Very pleased. Initially ordered 1 pack to check them out and take cost of repairs slow. Price is unbeatable especially with quality. I was so pleased with quailty I immediately ordered another pack. Super fast delivery. Listing says 10yr warranty. Panel wrap said longer? Hopefully won't be needed anyway. Now looking to upgrade doors and walls over time just for a better insulation against Texas heat or cold. For reference I run heat or a/c as needed and run year round. Harbor freight original panels are 4mm these are twice insulation at 8mm. I also use 2 self-taping metal screws to anchor panels to frame. Hope that helps save some greenhouses!