Notes for chapter 7
In a little twist to the tale, it seems someone in the Radley household has realized the children are interested in them. On their way to school, someone drops gifts for them - chewing gums, toys etc, which they gladly pick from a hole in a tree. But the day the kids, Scout and Jem, decide to write a "thank you" note to the individual, the gifts stop and the hole on the tree is filled with cement. The kids discover it is Nathan Radley who filled the hole with cement. It makes Jem to cry.
I think the author is trying to make us see something about the character of Nathan Radley. Maybe he loves children but doesn't want anyone showing kindness towards him. The next chapters might reveal this conjecture.