The “glass castle” is a dream that the father, Rex Walls, has. Rex keeps telling his family that he is going to build a glass castle for them in the near future. The glass castle symbolizes the Walls’ family at this point. The Walls’ family is fragile and hard as a rock at the same time. The reason that they are fragile is because their glass, they become poor at some points and they don’t have a lot of things other families have. The Walls’ family is also like stone. Their strong and smart, they know how to get bye in life with what they have.