Definition B: A posted command, warning or direction.

B7: The modern day pictogram of an arrow found in a number of public places traces its roots to one of the earliest families of signs in the world. As a pictogram it is thought to be linked to the small black footprints found on ancient Aztec codices and the Victorian pointing hand, with one finger protruding. A more obvious link is following the flight of an arrow in battle as the signifier to show the way as the signified.