If you mean the thick bar with a "claw", almost level with and parallel to the hull floor, then it is a tow bar, as Gordon has correctly surmised.
If you mean the thing that arises from the track and is truncated by the picture top, then something niggles me into believing it is a very narrow slice of a background utility pole, note what appears to be a wire going from the tow bar to the upper right, possibly intersecting with the utility pole above the picture top. It's just something about it that reminds me of frame type utility poles (telephone, telegraph, electricity?) seen in some South of France wartime shots.
If you mean the thing that arises from the track and is truncated by the picture top, then something niggles me into believing it is a very narrow slice of a background utility pole, note what appears to be a wire going from the tow bar to the upper right, possibly intersecting with the utility pole above the picture top. It's just something about it that reminds me of frame type utility poles (telephone, telegraph, electricity?) seen in some South of France wartime shots.