Symbolism, Imagery, Allegory
You know how in The Addams Family there's the Hand that creeps and crawls over everything independently?
Okay—now switch gears because that's the opposite of what hands are like in this novel. (And, yes, that was our cheap ploy to get you to read on.)
Hands in A Step From Heaven aren't independent at all—they're extensions of the characters. In fact, the most common way the book introduces the hand (especially Apa's hand) is through the onomatopoeic (yeah, we can get literary on you too) slap every time Apa hits someone. So in other words, we know the hand through what the character (again, usually Apa) makes it do—it's kind of like an action figure that only comes alive once you move it around.
We don't just see the bad in characters through their hands though, and in the hands of other characters (get it?) like Uhmma, hands become evidence of their strength:
Uhmma's hands are as old as sand… They knew how to make a medium-rare steak, baked potato on the side, in ten minutes flat for hungry customers always in a hurry. Uhmma's hands washed our dinner dishes, cleaned the kitchen floor with a rag, folded load after load of laundry… Uhmma's hands rarely rested. (31.1-3)
Note, by the way, that these hands are kind of independent since "they [know]" how to do all sorts of things—they still belong to Uhmma of course, but Young Ju is giving them the respect they deserve by treating them like the precious little helpers they are. After all, "Uhmma's hands have lived many lives" (31.17), and without them Uhmma would never have been able to raise her family in America. They are what allow her to labor—a major deal in a book that totally values hard work.