Thieves' Symbols

To cope with the uncertainties of hobo life, hobos developed a system of symbols, or a visual code. Hobos would write this code with chalk or coal to provide directions, information, and warnings to others in "the brotherhood". A symbol would indicate "turn right here", "beware of hostile railroad police", "dangerous dog", "food available here", and so on.

For more information on this symbolic written language, check out the following links:

https://en.wikipedia.org/wiki/Hobo#Hobo_signs_(symbols)

http://www.angelfire.com/folk/famoustramp/signs.html

https://owlcation.com/humanities/All-things-HOBO-signs-and-symbols