Wall panels

摘要

Disclosed is a constant contact panel interlock even during thermal expansion and contraction by providing flexible pins to bear on a tongue in a tongue and groove interlock and also by providing ramps for a bendable flange to slide over and bear on. Further, a material made of polypropylene with 20% calcium carbonate filler is used to form the panels, such material being sufficiently flexible at the temperatures common for panels exposed to direct sunlight (as on a roof or wall) to permit the pins or flange to bend without breaking and also being a material of much lower coefficient of expansion than pure polypropylene.