The wall is used by Shevek as an image throughout. It is his goal to break down walls that separate humanity on the different planets. In some scenes, the wall is literal, meaning it actually exists. In other scenes, the wall is figurative or symbolic. Just think of what the literal wall does; it is used to separate rooms in a house, etc. Then when you think of the symbolic wall, consider what ideas or beliefs are being separated and how it affects the meaning of the literature. Walls are also used in Shevek's dreams.