Up on the roof, the plastic bubbles on these tubular skylights are designed to let in light from all directions, with special enhancements to grab the most light when aimed to watch the sun's path across the sky during the day. The black base is sealed underneath with rubberized, waterproof roofing cement to prevent water leaks. Here I've improvised a foam pool toy to help fill the gaps in the customer's corrugated roof, to save them money and conserve the specialized roofing cement.