The Pigpen Cipher was used by Freemasons in the 18th Century to keep their records private. It was also used by Union Prisoners in Confederate prisons during the American Civil War. The cipher does not substitute one letter for another; rather it substitutes each letter for a symbol. The alphabet is written in the grids shown (see picture below), and then each letter is enciphered by replacing it with a symbol that corresponds to the portion of the pigpen grid that contains the letter (Singh 1999).
If I wanted to send the message "BEWARE" I would write the following symbols:
