Weathertight. The ClamDoor is a lightweight fiberglass alternative to traditional basement bulkheads. According to the maker, the design incorporates elements of sailboat technology. The hatch lid is held open with pneumatic lifters, and it seals closed with a flexible gasket. The gel-coat finish can be painted or left as is. The product comes in 64- and 72-inch lengths and costs $1,490 and up. ClamDoor, 888/344-2526, clamdoor.com.