The wall can be seen as a symbol in a couple of ways. The first is that a wall, itself, is a type of barrier. When I think of a "wall," I think of a partition, a form of dividing oneself or elements from one another. Certainly, the wall can be seen as representing this in the story, as the family, specifically the mother and father, become obsessed with keeping their family safe. This vision of "safety" is one in which the outside world is repelled, kept at a distance. The family recognizes this as the outside world is seen as one rooted in lawlessness and chaos, elements that the family wishes to keep away from their own consciousness. The wall is a part of that. The fact that the wall itself was designed to keep the outside world away from the family, or keep the family cut off from the outside world is representative of this idea of partition and separation. This is enhanced by the shards on the top of the wall, designed to prevent anyone or anything from seeking to climb it. Finally, the wall's addition of the barbed wire trapping on the top of it is the final element that displays to what extent the family will go to ensure that the outside world is "walled" off from them or that the wall itself keeps the family "walled" off from all that is on the outside. It is here where the wall operates as a symbol, a representation of how alienated the family ends up becoming both from the outside world and their own sense of happiness as demonstrated with the ending of the story.