He turned round so that his fingers might feel the grated opening.

The edge of the little bars was sharp.

He placed the strap binding his wrists against these sharp edges, and drew his arms up and down, a difficult and painful business.

The iron cut his hands and wrists at first, so awkward was the movement.

But, steeling himself, he kept on steadily.
At last the straps fell apart, and his hands were free.