What literary techniques can be found in the following quote from To Kill a Mockingbird by Harper Lee:
I drew a bead on him, remembered what Atticus had said, then dropped my fists and walked away, "Scout's a cow--ard!" ringing in my ears. (Ch. 9)
In Scout's narrated passage above found in Chapter 9 of Harper Lee's To Kill a Mockingbird, the first literary technique can be found in the very first clause, "I drew a bead on him," which is an idiom. Idioms are expressions found in phrases of "two or more words" that cannot be interpreted literally because idioms have a deeper or different meaning from the literal meanings of the words in the phrase (Literary Devices, "Idiom Definition"). In fact, it can be said that idioms have metaphorical meaning, so, like metaphors, idioms are a type of figurative language.
When Scout thinks to herself, "I drew a bead on him," she is obviously not literally drawing a picture of a bead on Cecil Jacobs, who has insulted her by saying her "daddy was a disgrace" and that Tom Robinson should hang. Instead, the term bead can also be used to mean bullet, and in North America, the phrase "draw a bead" has come to mean to take aim at someone/something or to very, very seriously focus your attention on someone/something, in the same way you would focus your attention if you were about to shoot. Scout, however, is not literally about to shoot. She is instead simply saying that she focused all of her attention on Cecil Jacobs.
A second literary technique can be seen in what Scout hears as Cecil's reply: "Scout's a cow--ward!" Here, Lee intentionally has Cecil break the word coward up using a dash. The use of the dash can create two different effects. First, it emphasizes the word cow, so that Scout hears herself being called a cow, which would further insult her. Second, it draws out the word coward, which lets the readers know Scout heard the word coward "ringing in [her] ears" for an exceptionally long time. The extension of the word coward helps the reader to empathize more with Scout's feelings at this moment in time.