This is one door out of a set of two which separate the net when it is set off of the stern of the trawler(dragger). The chains you see are attached to the cable wire which is released from the winch. Then the net is attached to the doors to get the spread needed to maximize the area of open net and snare as much fish as possible.
Dragger Pamet Door, originally uploaded by captjoe06.
Good Morning Gloucester 