The previous post is quite accurate in the assertions made. I would also bring to light the idea that "partitions" and "divisions" are critical element in the concept of fences and Wilson's play. If the fence is removed from the set, the physical representation of what Troy wishes to do to death, to pain, to emotional guilt, to responsibility, and to his own affective state of being is absent. Part of the reason why the title is so effective with the physical object of the fence is that this is what Troy thinks of his life. Fences are divisions, partitions, that he uses to keep the world at bay, to keep away the pain that he experiences, and to avoid direct examination of his consciousness and the choices that have defined it. When Troy seeks to keep death out, it is an obvious call out to create a metaphysical fence and to see it on stage in a way explores the futility of such an action.
Well, if the setting were changed, then the title would have to go. It couldn't be called Fences without a fence.
It's got to be in the back yard, where fences go. Troy and his people have been in the back of things their whole lives. Troy has worked the back of the garbage truck: he picks up garbage from the back of white people's houses. Blacks had to sit in the back of restaurants and ride in the backs of buses.
You can't very well call the play anything else. It can't be staged on a front porch. That's not where people drink on Friday nights. That's not where you swing a bat or where you saw wood. The front yard or porch has no such connotations. It has no fences, secrets, or social barriers. It doesn't keep people in or out.
Fences is built around fences--literally. The fence is always on stage. Remove it and you have no play.