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 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 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 he reminds Troy of how much Rose loves him, and what a good woman she is. 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.
In a moment of compassion, Bono spells out to Cory and Troy the reason that Rose wants the fence built. Bono sees the fence as a defining symbol of her qualities as a wife and mother; she fears that her family's relationships are falling apart, and she hopes the fence will keep her loved ones close to her. 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 is meant for 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 following his dreams.
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.
Bono's poignant observation of Rose's desire to keep her family together leads to Troy admitting the truth about his affair. Troy's confession to Bono leads to the rising action of the play, culminating in Troy's admission of his affair to Rose. Until this moment, Troy has lived in denial about his affair, allowing himself the luxury of believing in and escaping to a world of illusions with Alberta, separate from his real-life responsibilities and disappointments. By announcing the truth out loud to Bono, Troy begins to fully understand the enormity of the betrayal he has committed. Unfortunately for Troy, he is too late: Alberta is now pregnant with his child.
Unfortunately for Troy, his timing is too late. Alberta is pregnant, creating another realized form of his betrayal that will not be erased. Troy and Rose argue about Gabe's recent arrest and decision to move out, driving the rising action forward and steeping Troy and Rose in the unsatisfying bickering of their failing relationship. Rose's involvement in Gabe's life also expresses how closely linked Troy's family is with her own life, a stark contrast to the lover, Alberta who is a stranger with no familial duties. Troy blurts out to Rose the fact of his affair with Alberta in a double dose of shocking betrayal. He does not first reveal his affair and then the pregnancy, but dishes both parts of his news at once saying to Rose, "I'm gonna be a daddy." Rose demands an explanation and Troy, still clinging to a world of illusions and selfish excuses, only provides Rose with indulgent reasons why he needed to be with Alberta, and never apologizes for his decision.
Rose and Troy's disparate outlooks on how to live their life come to a head here. When Troy explains that having the affair felt like he was achieving something instead of remaining stagnant in a dead-end career and failing relationships at home by describing the decision as stealing second, like the move in baseball, Rose snaps at Troy in an effort to ground him in the reality of his mistake. She says, "We're not talking about baseball! We're talking about you going off to lay in bed with another woman!" Troy continues to see the story only from his point of view with no comprehension of the effect his actions have on anyone but himself, even when his actions will soon bring a new life into the world and change the life of those who are closest to him forever.