How does Ken Follett use imagery in A Place Called Freedom?

Imagery:

"It's here on my desk, beside the computer. I use it as a paperweight. I often pick it up and turn it in my hands, rereading that inscription. If the iron collar could talk, I think to myself, what kind of story would it tell?"

"Mack lay in the hold of the Rosebud, shaking with fever. He felt like an animal: filthy, nearly naked, chained and helpless. He could hardly stand upright but his mind was clear enough. He vowed he would never again allow anyone to put iron fetters on him. He would fight, try to escape, and hope they killed him rather than suffer this degradation again."