Theif organisations and guilds usually have an identifying mark or symbol, after all thiefs may not like to be famous, but (in)famous would be nice.

Shadow Heraldry is the practice of identification between guilds using that insubstantial friend if the thief. Its can be a mix of innocious thing that when backlit cast a shadow which forms an object or collection, or something as simple as hand shadows. In a thiefs guilds lair a number of objects may be attached to a torch bracket, the troch flame will projets the objects shadow onto a wall, individual or chair. The objects, for instance may be kinfe and horse shoe, projecting the shadow emblem of the Moon Sword guild. The Moon Shadow guild has for instance a simple black creasent to represent the moon, this in turn is used by thiefs on the streets by forming a "C" shape with one hand. Two thiefs may interlock creasents, hence acknowladgeing each other. The two thiefs in question do not even have to be on the same side of the room ( or street ). One may be standing at a bar, the other seated by the fire place opposite. The first theif will see the projected creasent of the seated thief and scratch his head in order to form the acknowladgement. They need not even make eye contact. It is quick and simple and has many other user. It could for instance be used to pin point someone in a room who is to be assinated.