What are the shared features of firemen?
All the firemen have the same basic physical appearance. They all look slightly sun-burnt from spending their days starting fires and watching them burn. They all have "charcoal hair and soot-colored brows and bluish-ash-smeared cheeks where they has shaven close; but their heritage showed." Montag realizes as he's looking at a group of firemen that they all look the same, including himself and he's never really stopped to take note of it until now. It's as if they were all predestined to be firemen based on these characteristics.