Cory hits the baseball tied to the tree in the yard. When he sees Rose, he tells her that he isn't quitting the football team. Rose agrees to talk to Troy on Cory's behalf when Troy comes home from bailing Gabriel out of jail. Gabe was arrested for disturbing the piece. It cost Troy fifty dollars to bail out Gabriel. Troy and Bono believe that the police arrest Gabriel often because it is easy for them to take him and it makes them a quick fifty dollars. Bono and Troy work on the fence together. Bono complains that the wood is too hard and difficult to saw through. Bono asks Troy about his relationship with Alberta again. Bono says that he they have "done got tight," or closer to one another. Troy denies Bono's accusation. Cory joins them and cuts through the wood easily.
Cory and Troy do not understand why Rose wants a fence built. Bono does know why, and explains to Troy and Cory that Rose loves her family and wants to keep them safe and close to her love. Bono tells Troy and Cory that people build fences for two reasons: "Some people build fences to keep people out and other people build fences to keep people in." Bono does not mention Troy's mistake of having an extramarital affair in front of Cory but shares his opinion on what Troy should do through his explanation of the fence. Bono implies that Troy should respect Rose's love and be loyal to her love instead of pushing her and Cory away from him.
When Cory goes into the house to look for a saw, Bono confronts Troy more explicitly about his affair. Troy finally admits to Bono that he is indeed having an affair with Alberta. Bono wants Troy to stop the affair before it's too late and Rose finds out. Bono bets Troy that if he finishes building the fence for Rose, Bono will buy his wife, Lucille the refrigerator he has promised her for a long time. Bono decides to go home and not help troy with the fence anymore.
Rose asks Troy about what happened with Gabe at the station. Troy tells Rose about the fifty dollars and a hearing in three weeks to determine whether or not Gabe should be recommitted to an asylum. Troy explains to Rose that Gabe was arrested "for howling and carrying on" after he chased some kids away who were teasing him. Troy and Rose argue over whether or not Gabe needs more supervision.
Troy suddenly tells Rose that he is going to be a father to a child of another woman. Gabriel shows up at the house and interrupts their important conversation. Rose becomes upset and outraged. She cannot believe that she has been loyal to Troy for eighteen years and he has done this to her. Gabriel senses that Troy has done something wrong to Rose. Gabe compliments Troy on helping him earlier that day at the police station. Troy expresses to Rose that he spent time with Alberta to escape. Rose believes she has been a good wife and mother and so Troy should have stayed with her. Troy selfishly conveys to Rose that he used Alberta to get away from the pain of his stagnant career and life goals. Rose rebuts his excuse by asserting that she invested her whole life in Troy, even when she knew he wasn't going anywhere. Rose feels just as stuck as Troy but she hasn't hurt Troy the way is hurting her. Rose accuses Troy of being selfish and of taking and not giving. This makes Troy very upset and he grabs Rose's arm. Rose yells at Troy because he is hurting her arm. Cory hears the noise from inside the house. He comes outside and surprises Troy by grabbing him from behind. Cory punches Troy in the chest, knocking Troy to the ground. Both Troy and Cory are surprised at Cory's actions. Troy lunges at Cory but Rose holds him back. Troy collects himself and yells at Cory instead of hitting him. Troy tells Cory that he just committed strike number two, and leaves the yard.
Bono clarifies the significance of the play's title as the action rises and nears the climax of the scene. In a profound moment of compassion, Bono spells out to Cory and Troy the reason Rose wants the fence built. His reason is a metaphor not a literal interpretation. Bono sees Rose's fence as a defining symbol of her qualities as a wife and mother, correctly fearing her family's relationships are falling apart. Bono observes that the fence is symbolic of both the negative and positive aspects of the Maxson family. His reference to the people who build fences to push people away from them is indirectly directed at Troy who, with his affair, will eventually hurt his wife and who is already in the midst of hurting his son Cory by preventing him from a hopeful future. We never learn the practical reason why Rose wants the fence built. Perhaps she wants Troy and Cory to bond while making a fence together. Perhaps she thinks it is a way to keep her eye on Troy. Wilson never allows us into that part of Rose's thinking, so the fence, like Bono's description, leaves the observer to interpret the meaning of the fence for themselves.