a discreetly obvious brass thieves ' guild plaque over the door told the world that mr goriff had conscientiously paid his annual fee , 7 but the world had plenty of less formal dangers and so vimes took a piece of chalk out of his pocket and wrote on the door : under the protection of the watch as an afterthought he signed it : sgt detritus in the imaginations of the less civically minded the majesty of the rule of law did n't carry anything like as much weight as the dread of detritus .