“Now and then a fellow gets to thinking about it. Not often, though. Which is a good thing. For the Lord aimed for him to do and not to spent too much time thinking; because his brain it’s like a piece of machinery: it won’t stand a whole lot of racking. It’s best when it all runs along the same, doing the day’s work and not no one part used no more than needful.”
Faulkner, William. As I Lay Dying: The Corrected Text. New York: Modern Library, 2000. Print.
Faulkner’s characters often use similes; in the passage, the literary device serves not only as a comparison, but showcases Tull’s dialect, what with the lack of grammar in “because his brain it’s like a piece of machinery,” (a comma is needed here) and “not no one part used no more than needful” (rather than saying, “not using any more parts than necessary.”) Language is the foregroun to Tull’s perspective. It’s what gives him his particular “voice.”