Hands are a very significant body part throughout this novel, and seem to symbolise both power and self-awareness. Note how Mama Day is described early on in the novel:
She could walk through a lightning storm without being touched; grab a bolt of lightning in the palm of her hand; use the heat of lightning to start the kindling going under her medicine pot. She turned the moon into salve, the stars into swaddling cloth, and healed the wounds of every creature walking up on two or down on four.
The reference to her being able to "grab a bolt of lightning in the palm of her hand" is highly significant, as it indicates both tremendous power and self-awareness, which are two qualities that Mama Day exemplifies.
However, when we come to the end of the novel, the importance of hands becomes far more explicit. When Mama Day realises that Cocoa has transferred a significant element of herself into George's hands, she realises that George must link hands with Mama Day and make a "bridge for Baby Girl to walk over." His failure to do so indicates both his own lack of power and self-awareness about his identity. This is only something he can overcome through his own death, which allows Cocoa to live. Hands therefore are particularly important in the resolution of this novel and in terms of showing characterisation.