As the two-day Group of 20 summit brought together leaders of the world’s industrialized nations to Pittsburgh, the police were out in force, patrolling on bikes, on foot, on horseback, by river and by air. Along Forbes Avenue, Fifth Avenue and outside the Carnegie Library, small bands of protesters began milling around the streets preparing for processions that had not sought official permission. Organizers urged them to write the phone numbers of local lawyers on their bodies in case of arrest.