The Hobo Code

There's nothing cooler than a secret alphabet. From Wikipedia:

To cope with the difficulty of hobo life, 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. For instance:

• A cross signifies "angel food," that is, food served to the hobos after a party.
• A triangle with hands signifies that the homeowner has a gun.
• Sharp teeth signify a mean dog.
• A square missing its top line signifies it is safe to camp in that location.
• A top hat and a triangle signify wealth.
• A spearhead signifies a warning to defend oneself.
• A circle with two parallel arrows means to get out fast, as hobos are not welcome in the area.
• Two interlocked humans signify handcuffs. (i.e. hobos are hauled off to jail).
• A Caduceus symbol signifies the house has a medical doctor living in it.
• A cross with a smiley face in one of the corners means the doctor at this office will treat hoboes for free.
• A cat signifies that a kind lady lives here.
• A wavy line (signifying water) above an X means fresh water and a campsite.
• Three diagonal lines mean it's not a safe place.
• A square with a slanted roof (signifying a house) with an X through it means that the house has already been "burned" or "tricked" by another hobo and is not a trusting house.
• Two shovels, signifying work was available (Shovels, because most hobos did manual labor).

The image of wandering people finding their way by reading the mysterious symbols scratched by those who came before makes me want to tell a story. Maybe a ghost story, about an abandoned station at a western ghost town, where strange markings left by earlier victims warn others away lest they become prey for the spectral beast. Or a more ambitious story with a secret community hidden in the mountains, welcoming to all who can unravel the clues and reach it, with unknown enemies known only by frightened symbols scratched by those who disappeared, with some sort of treasure or revelation hinted at by symbols none of the living can understand.