Chalked on a fence, the symbol seen here warned fellow hobos of the presence of one of these
The code 
underscores the vaguely amoral lifestyle of hobos, one guided... [DOC] [TLE] The American boys' book of signs, signals and symbols [PAR] hoboes, tramps, yeggmen, gypsies, and the American Indians, ... these signs lies 
in the fact that if one understands the symbol, ...