For my maritime friends, here's a reminder of the International Flag Code regarding infectious disease. I'm displaying the checkerboard Lima signal because, while I'm healthy today, I'm not requesting "free pratique." I prefer to be treated as if I were under quarantine. Back off and keep space, please.
Signal flag "Quebec, " also called the "Yellow Jack" is a simple yellow flag that was historically used to signal quarantine (it stands for Q), but in modern use indicates the opposite, as a signal of a ship free of disease that requests boarding and inspection.Plain yellow, green, and even black flags have been used to symbolize disease in both ships and ports, with the color yellow having a longer historical precedent, as a color of marking for houses of infection, previous to its use as a maritime marking color for disease. The present flag used for the purpose is the "Lima" (L) flag, which is a mixture of yellow and black flags previously used. It is sometimes called the "yellow jack" but this was also a name for yellow fever, which probably derives its common name from the flag, not the color of the victims (cholera ships also used a yellow flag).The plain yellow flag ("Quebec" or Q in international maritime signal flags) probably derives its letter symbol for its initial use in quarantine, but this flag in modern times indicates the opposite—a ship that 'requests free pratique', i.e. that declares itself free of quarantinable disease, and requests boarding and routine port inspection.
You're welcome to post the Lima flag with or without text on a window to let visitors know your stand. Click the images below for PDF. Dot, dash, dot, dot.