Ernest Tilley and Bill "BB" Babowsky are "tin men" door-to-door aluminum siding salesmen in Baltimore in 1963. Working for different companies, they are prepared to do almost anything legal or illegal to close a sale. BB buys a shiny Cadillac to maintain his image of success and almost immediately crashes into another Cadillac driven by Tilley (all "tin men" drive a Cadillac). It is not clear who is at fault for the accident (BB is entering the public way from the dealer, in reverse but very slowly; Tilley has the right of way, however, he was clearly distracted). This generates a spate of road rage and the two rivals vow to do anything to get back at the other. BB seduces Tilley's wife as an act of revenge, not knowing that Tilley wants to leave her anyway. Exhausted by their rivalry, the two men decide to play a game of pool to decide who should get her. BB loses, but he does not honor the bet.
The then newly formed Maryland Home Improvement Commission is charged with uprooting corrupt sales practices in the home improvements industry calls both men before them and takes away their licenses. Reconciled to their fate, the two men start planning new business deals together.