You can install our Deck Top Roof Tiles without dowels or with dowels. It just depends on what method of install that you prefer. We recommend using the dowels as not to damage the rubber membrane roof surface. Also when using the dowel method, the floor is more of a floating floor, so if there were any issues with your roof, you can remove the tiles, fix the issue, and then replace them. If you are looking for a more permanent installation and don't have any concerns with your roof being damaged, you can glue the tiles down.