How does the author use symbolism in the novel, The Water Cure?

One example of symbolism can be seen in the author's use of the barbed wire fence to represent the family's isolation and fear of the outside world. Grace explains the fence's purpose: "Should anyone arrive on the island, it serves the same purpose as the buoys out in the bay, marking out a clear message. Do not enter. Viewed from another angle, Do not leave" (41). Thus it is never really clear how much the fence is meant to keep the outside world away and how much it is meant to keep the girls inside. At the end of the novel, Grace, Lia, and Sky bend tree branches over the fence in order to safely escape the confines of their former home and begin their new life.