This page lists all the various symbols in the Hobo signs category.
A hobo is a migratory worker or homeless vagabond—especially one who is penniless. The term originated in the Western (probably Northwestern) United States around 1890. Unlike "tramps"—who work only when they are forced to- and "bums" who do not work at all, "hobos" are itinerant workers.
It is unclear exactly when hobos first appeared on the American railroading scene. With the end of the American Civil War in the 1860s, many discharged veterans returning home began hopping freight trains. Others looking for work on the American frontier followed the railways west aboard freight trains in the late 19th century.
To cope with the difficulty of such a lifestyle, hobos developed a system of symbols, or a code. Hobos would write this code with chalk or coal to provide directions, information, and warnings to other hobos. Some signs included "turn right here", "beware of hostile railroad police", "dangerous dog", "food available here", and so on.