I love this book. i suggest u just talk about their character traits in sentences.
The mockingbird symbolizes the innocence of the certain characters
It seems that you have missed the necessary options for us to complete this analogy, but hope this one helps. So if thread is to string, therefore, a cask is to barrel. A cask is a <span>large barrel like container made of wood, metal, or plastic, used for storing liquids especially those with alcohol. Hope this answers the question.</span>
So, just to clarify, your essay is circled around the quote at the bottom? What work of literature are you going to use?