Paul Erdos, like many mathematicians, was an eccentric. He wasn't interested in money, and gave what little he made to beggars and various strangers. With no family, job, nor hobbies to speak of, he dedicated his life to math. Nor did he ever have his own address. Rather than purchase a home, he instead moved around within a network of friends worldwide with which he stayed. He would just come by without calling beforehand and announce, "My brain is open!" His motto? "Another roof, another proof!"

Of course, most of us don't live a transient, mathematical lifestyle like old Paul's, and as such must deal with the practicalities of roofing, of maintaining our roof, of protecting it, of, basically, keeping it from falling down on our heads. But how do you keep your roof in good shape? Easy