Uncle Hammer is Papa's brother, and uncle to Cassie, Stacey, Little Man and Christopher-John. He comes off as a "city slicker" when compared to the other country folks: he lives in Chicago (the Big City), he dresses "nattily" (a cool word you don't see too often which pretty much just means "snazzily"), and drives around an expensive luxury vehicle (a Packard, just like Mr. Granger).
Uncle Hammer is an example of a black man of the time who has definitely "arrived." His status symbols (fine clothing and nice new car) come from the good job he has in Chicago:
Up there I got me a man's job and they pay me a man's wages for it. (7.165)
Of course, Mr. Granger doesn't approve of this, and accuses him of being right "citified" and of thinking he's "too good to work in the fields like other folks" (7.166).
But Uncle Hammer just wants to be paid fairly for his work. And we don't blame him for not wanting to take the fifty cents a day that the fieldworkers and day-laborers make in the South. Uncle Hammer's situation shows us that blacks are treated more fairly during this time in the North than they are in the South.
Those economic realities led to the Great Migration—rural African Americans left the South in huge numbers, settling in industrial cities all over the county. And after reading this book, we're surprised anyone stayed behind.
Thanks to his experiences up North, Uncle Hammer doesn't take business from anyone. When he sees injustice done to his community, he wants to shut that nonsense right down—like someone pounding down a nail with a hammer. Hmmmm…hammer…Uncle Hammer…Coincidence? We think not.
Consider how Mr. Morrison has to talk Uncle Hammer down after he finds out that Cassie has been pushed around by Mr. Simms. Here's his justifiably angry response:
You think my brother died and I got my leg blown off in their German war to have some red-neck knock Cassie around anytime it suits him? (6.56)
Yep, it's pretty clear he wants to run out and knock Mr. Simms right back. Plus, he has a gun, which could totes complicate the situation. And did we mention he's impulsive? Uncle Hammer initially wants to re-pay violence with violence. His preferred tactic provides a sharp contrast to Mama's more peaceful methods (the boycott of the Wallace store).
But, Uncle Hammer reins in his impulsive behavior toward the end of the novel. When Mr. Granger is about to foreclose on the Logan land, we expect Uncle Hammer to come up from Chicago and go all 1930s Punisher on him. Instead, he sells his snazzy car to help pay off the bank loan. And then leaves town to doubly make sure his anger won't spill over.
Good choice, Uncle Hammer.