Forgefix carcass screw pozi sct black phosphate forgefix cars4245 these forgefix pozi carcass screws have an extremely coarse single thread the have a black phosphate coating for increased durability and a self drill point for easy installation designed specifically for chipboard and mdf medium density fibre board and carcass assembly phosphate coatings are made up of thin crystalline layers of phosphate compounds that adhere to the surface of the fixing or fastener the phosphate crysta