These strange symbols are the way hobos passed information on to the next guy (usually a guy, but as Willy pointed out, he did meet his first wife on the road). And as the chart below shows, hobos had a lot to say. They scratched out simple instructions about which direction to go or where’d be a good spot to catch a train, but the marks could also communicated elaborate details about the town (the police don’t like hobos here) or the homeowners (they’re an easy mark).
https://www.popularmechanics.com/technology/a25174860/hobo-code/