In “the pit and the pendulum,” how does the narrator escape the pendulum?

In "The Pit and the Pendulum," the narrator finds himself tied down flat, with a sharp pendulum slowly swinging downwards towards him.

He finds that he is unable to untie himself.

Earlier, he was given food, containing meat, and that food is within his reach, though he is tied down. 

He finds rats are in the cell with him, so he devises a plan.

He takes the meat from his dish and rubs it all over the ropes tying him down. The rats then jump up onto him and begin gnawing on the ropes. Eventually, he is able to split the chewed ropes and free himself.

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