Who is Frank (the chauffeur) from Hollywood: A Novel and what is their importance?

Frank is the chauffeur who, in a fashion that Chinaski finds amusing, speaks irreverently about both Hank himself and the Hollywood life in which they are both peripheral participants. At one point, Frank drinks from a bottle of wine while driving, which makes the evening (as Hank calls it) "interesting". Frank represents a spirit of rebelliousness, of independent thought and action that Hank, in spite of his evidently increasing sense of domesticity, still enjoys in others.