The device is made of thick hard plastic. I installed it by drilling 3 holes for the #10 x 1 inch button head screws. I used butyl tape between the element and the roof to minimize the chance of leakage. I will use Dicor Lap Sealer on the seams for extra waterproofing. The only complaint is with the cable attachment: as the ends have to be tightened to squeeze the seal around the cable, if not very careful the entire attachment can come loose as the attachment is held in place by two plastic nuts. (One on each side of the unit.) I think I can end up using PVC glue to hold the inner nut in place. This way the mounting gasket can't slip and come loose (it's not waterproof).