Each street gang has its own unique signal, sign, colors, jewelry and dress. These serve to identify gang members and to promote solidarity. Each gang vigorously protects its symbols from insults by rival gang members. The greatest humiliation for a gang is to have one of its symbols degraded. If you see an emblem or symbol displayed upside down, it is a degradation to that gang and was most likely written by a rival gang member.
Many people falsely assume graffiti represents thoughtless vandalism.
To the gang member, graffiti is a clear marking of territorial boundaries and serves as a warning and challenge to rival gangs. Graffiti can be found anywhere. It is most commonly found on garages, business walls, schools, abandoned buildings, and bedroom and basement walls of gang members. The purpose of all gang graffiti is to glorify the gang. Gang members employ several means of non-verbal communication to acknowledge their gang or to challenge rival gangs, including hand signals.