Zulu is made of 4 isosceles triangles - yellow, blue , red, and black in clockwise order from the top, and stands for "Z" in the signal flag alphabet. I know exactly how this one was made. These were the leftover scraps, the flagmaker said "Foxtrot this, we're on Z," so he just threw them together. If it makes the entire process 1/26th less wasteful though I'm all for it.
If you're in a harbor and it isn't safe or legal to operate under your own power, or even if your engine is out, fly this flag to hail a tugboat. Having never needed a tugboat myself, I'm wondering if it's like a cab/Uber situation. Like look on Tuber first, and if there's a surge THEN put up the flag for a tugboat.
If you're a fishing vessel, throw this flag up when you start shooting out your nets.
When displayed with numbers, Zulu is used to signify the time. The first two digits are hours, the last 2 are minutes. This may have been used for a brief period of time when having a watch was considered "really cool" and captains wanted to brag to each other.
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