Unusual symbol on barge cranes

October 22, 2018 10:27 AM

There are cranes on barges working alongside the Bay Bridge; the cranes each have some kind of metal symbol on the top of them, behind the gantry. Here is my very crude illustration of what I'm talking about. What is that symbol/sign thing? NB: It's a little smaller than is represented in my drawing, but definitely circle-diamond-circle, and flat black in coloring.
posted by salt grass to Grab Bag (2 answers total)

Best answer: Those are maritime day shapes. I've been retired for a while, but I still instantly remembered that BALL-DIAMOND-BALL is the configuration for "Restricted in ability to maneuver." It is a signal to other ships to steer clear-- the barge is doing something (probably dredging) and it can't move around as much as it normally can.

Source: 12 years at sea. They are made of black fabric and metal rods, and you put them up in different combinations to send different messages. At night you use lights for the same thing. I have put many of them together in my life, and hoisted them aloft many many more times. Memories of time that won't come again (I hope).
posted by seasparrow at 10:30 AM on October 22, 2018 [115 favorites]

Response by poster: Boom! Thank you very much, seasparrow!
posted by salt grass at 10:37 AM on October 22, 2018