The following lines appear in the Anglo-Saxon poem The Wanderer:
as now here and there across this Middle-Earth
blown on by wind walls stand
In this stanza, the narrator is speaking about what a wise man must come to understand before he can be considered wise. In the lines in question, the wall symbolizes the barriers men must face and overcome when he realizes that the entire world will lie in waste.
Throughout the poem, the narrator speaks to the fact that the Wanderer has been forced to face many different challenges in life. He has lost his king, his kinsmen, and his home. He has been forced to climb many walls in order to find the one thing in life that will, for lack of a better phrase, "make the world a better place" for himself.
In the end, the Wanderer comes to find out that there is only one thing that one can depend on to survive forever: faith. In order to come to this, the Wanderer needed to climb many different walls.
The wall represents two very different things. First, it represents the literal physical walls the Wanderer comes upon during his travels upon the sea.
Second, the wall is a figurative concept that symbolizes the mental walls the Wanderer must scale in order to find security.