The above code was developed in 2007 by Emily Read in conjunction with charitable magazine The Pavement as a means for homeless people to 'review' amenities and share their experiences with other rough sleepers.
The code is printed inside each issue of The Pavement, which is then circulated widely around the homeless community. As editor Richard Burdett explains: "The guide fits in well with what The Pavement was founded for; allowing homeless people to make informed choices about their lives and what they do day-to-day.
Richard is keen to know if the code is working. Have you noticed any of these symbols chalked up on walls or paving stones?