What powerful language techniques/tools are used in To Kill a Mockingbird to construct character in the novel?

Harper Lee is able to give the reader a powerful image of the characters in the novel using very few words. Here is her description of Atticus in the first chapter of To Kill a Mockingbird:

"Atticus's office in the courthouse contained little more than a hat rack, a spittoon, a checkerboard, and an unsullied Code of Alabama. His first two clients were the last two persons hanged in the Maycomb County Jail. Atticus...

Harper Lee is able to give the reader a powerful image of the characters in the novel using very few words. Here is her description of Atticus in the first chapter of To Kill a Mockingbird:

"Atticus's office in the courthouse contained little more than a hat rack, a spittoon, a checkerboard, and an unsullied Code of Alabama. His first two clients were the last two persons hanged in the Maycomb County Jail. Atticus had urged them to accept the state's generosity in allowing them to plead guilty to second-degree murder and escape with their lives, but they were Haverfords, in Maycomb County, a name synonymous with jackass."

This description uses a great deal of irony and humor. Irony is a literary device in which the author presents the opposite of what the reader might expect. The idea that Atticus's first two clients were the last two hanged is an example of ironic humor. In addition, the idea that the state is generous in allowing the accused criminals to plead guilty is an example of ironic humor, as is referring to Haverfords as a form of "jackass." We know from this description that Scout's relationship with her father, Atticus, is tinged with a gentle humor. 

Later in the first chapter of the book, there is a description of Calpurnia: "Calpurnia was something else again. She was all angles and bones; she was nearsighted; she squinted. Her hand was as wide as a bed slat and twice as hard." Again, the author gives us a very good idea of this character with an economy of words by using metaphorical language. For example, Calpurnia is compared to angles and bones. Her hand is compared, using a simile, to a bed slat. Lee's use of well-employed metaphors and similes gives the reader a very good idea of Calpurnia's character and Scout's sometimes contentious relationship with Calpurnia in a few sentences.