Like Dagny, Hammond was in the transportation business (automobiles) before going on strike. Hammond's snazzy cars are actually featured in the novel more than Hammond himself, which is rather appropriate. Galt's philosophy says that people are defined by their work, so Hammond's cars are a fitting stand-in for the man himself. In Galt's Atlantis hideaway, Hammond runs the grocery store, which Dagny finds shocking. Hammond is providing an essential service, though: food. In the "real world" he provided the essential service of transportation, and his new role as a grocery store owner helps reorient Dagny to life in the valley, where any sort of useful work, no matter how unglamorous, is a good thing.