P was employed by an independent stevedoring company that was under contract to D to load its ship. The winch P operated was controlled by a ten-ton boom. One part of a freight car had been lowered into the hold. The second part weighed about eight tons. While it was being put down the shackle supporting the boom broke at its crown, causing the boom and tackle to fall and injure P. P sued D and two other companies. The District Court found that the shackle had broken as the result of a defect that had occurred in its forging. The two companies had purchased this equipment from another concern. Nevertheless, the court held they were negligent in not having tested it adequately before installing it. The court considered D to be under no such obligation to test and therefore not negligent. It gave judgment against the two companies but in favor of D. The Court of Appeals reversed as to D. It held that P should recover for the ship's lack of seaworthiness. D appealed.