The wall is a literal, physical wall. But it also is a metaphor for the emotional wall between the speaker and his neighbor. The speaker claims that something doesn't love the wall. The spring thaw and swelling ground makes the wall break down. The speaker implies that there is something in him (mischief) that also wants to break down the wall between himself and his neighbor. But the speaker fails to see how the wall actually brings him and his neighbor together every spring. So, the wall is something that separates and unifies. It physically separates and connects the two pieces of land. Metaphorically, it emotionally separates the two neighbors. But it can also be interpreted as emotionally joining the two neighbors: at least once a year to do the mending. The "mending" itself is also literal and metaphoric. They mend the wall but with this annual meeting they also have a sort of reunion and have the opportunity to mend their relationship. The speaker is convinced of his interpretation that the wall is a physical and emotional barrier. He thinks his neighbor is stubborn about the wall being sustained. The speaker doesn't consider that the wall serves a positive purpose as well: it gives him and the neighbor a reason to meet every year to mend the wall and their relationship. But the speaker dwells on his neighbor's supposed stubbornness and uses a simile to compare him to a type of caveman. "I see him there / Bringing a stone grasped firmly by the top / In each hand, like an old-stone savage armed." (A simile is a comparison of two things, usually using the words "like" or "as.") The speaker compares his neighbor to a savage. He believes his neighbor only values the wall as a means to keep the two men separate.