It is similar to a circle of salt but more powerful and persistent as it is usually etched or painted in place, and can't simply be brushed or blown away. If a demon walks inside the outer circle of a devil's trap, it cannot physically leave it, and is trapped. Devil's traps also inhibit the use of some demonic powers. Devil's traps have been used not only to detain a demon, but are also drawn at entrances as a deterrent to prevent access to a building, room, or container. The devil’s traps seen in Supernatural all originate from The Lesser Key of Solomon, which is a grimoire, or magical text, written in the 17th century. It contains rituals and spells for invoking and controlling both demons and angels.