As with any open ended fill in the blank question where options are not provided, I think that you could find many different approaches to the answer. I tend to think that the fire escape represents the idea of escape to many of the characters. This escape indicates that the characters feel trapped or imprisoned by the lives they lead. Tom certainly feels this. It is for this reason that escape is something that proves to be so elusive for him, something so powerfully a lure for him. Amanda escapes into her past, into a time when she was so much more than what she is. Laura escapes into the world of zoos and the glass menagerie, into a world that is so radically different from what she lives now. Even Jim escapes into a world of unfulfilled dreams and hopes. For these characters, the fire escape can come to represent that notion of liberating escape, freedom from a world of being pinned down by convention, responsibility, and the pain of dutiful obligation. In this, the fire escape can be seen as being symbolic of how each character feels trapped.