In chapter 4, Scout and Jem find two sticks of chewing gum and two Indian-head pennies. In chapter 7, the pair find an assortment of items consisting of a ball of gray string, two soap figurines, more chewing gum, a spelling bee medal and an old pocket watch.
"To Kill a Mockingbird," by Harper Lee, focuses on a 6-year-old girl named Scout, her brother Jim and the pair's interactions with a mysterious character known as Boo Radley. The items in the knothole of the tree are the children's channel of communication with Boo Radley, but the knothole is eventually cemented over by Nathan Radley. The story plays out against the backdrop of the Great Depression in Alabama. Scout and Jim's father, Atticus, is a lawyer who takes it upon himself to represent Tom Robinson. Tom, a black man, is accused of raping a white girl, which sets the stage for the examination of racial tensions that the book is famous for.
The book won a Pulitzer Prize, and the movie was successful at the Academy Awards.