Crooks stared hopelessly at her, and then he sat down on his bunk and drew into himself. She closed on him. “You know what I could do?” Crooks seemed to grow smaller, and he pressed himself against the wall. “Yes, ma’am.” “Well, you keep your place then, N----r. I could get you strung up on a tree so easy it ain’t even funny.” Crooks had reduced himself to nothing. There was no personality, no ego—nothing to arouse either like or dislike. He said, “Yes, ma’am,” and his voice was toneless.(pg 119)
Pressing himself up against the wall and making himself "grow smaller" reveals his vulnerability and that he is afraid of the power that others hold over him. He knows what could happen and is forced to bend to their abuse of their power. He reduces himself to "nothing" as if he has lost his own will.