ROOFER'S GOO is a term used to describe a combination of materials used by roofers to seal and waterproof roofs. The two most common materials used in this combination are TAR, which is a thick, sticky, black liquid made from coal, and PINETAR, which is a sticky, brownish-black liquid made from the resin of certain pine trees. Together, these materials form a waterproof seal that helps protect roofs from the elements.