What are five important symbols (tangible or intangible) in Bridge of Clay by Markus Zusak?

There are many symbols in the novel The Bridge of Clay written by Markus Zusak. Five specific symbols are: the bridge, the names of the pets, the clothespin, the piano, and Clay's book written by Michelangelo.
The bridge itself is a symbol for the work that Clay is doing to repair the relationships between his family members. This family was torn apart when their mother died of cancer, and Clay is determined to help his family heal.
The names of the Dunbar family's pets are also symbols. Each pet's name is the same as a character from Homer's writings. This is important because when their mother moved, she brought with her Homer's writings so that she could learn English.
The clothespin is a symbol of Clay's guilt for helping his mother commit suicide when her cancer became too painful. Clay carries this clothespin with him as a reminder of what he did and to remind him of the love he had for his mother.
The piano is a symbol of the love between the Dunbars. Penny bought this piano when she first moves. The piano is sent to Michael's house on accident and is the reason that they ever meet in the first place. Michael proposes by writing on the keys of the piano.
A last symbol is the book that Clay shares with Carey. This book belonged to his father during his first marriage, and it shows that Clay knows about his father's life because his mother shared the stories of their lives with Clay before she died.
All of these symbols represent the story of the Dunbar family.