A wall, fence, or other divider or barrier could have many different meanings, so consider its context and how you feel about it. Some possibilities are:
An obstacle or challenge
Something that keeps two people apart, such as a disagreement or being in different locations
Protection, separation, or an attempt to distance from another person or situation (as in "putting walls up")
An attempt to keep things out, or keep things in, contained, or controlled
A wall in a house can represent separation between the different parts of your life (for example, a house with no interior walls could mean you feel you have no boundaries between your work life, home life, and family life, etc.)