Posters, limited-circulation newspapers, excerpted press articles, pamphlets, and blackboard news using large-sized ideographs and mounted on walls as a popular form of communication. Used in China since imperial times but more commonly since literacy increased after the 1911 revolution. Used more frequently after 1949 to publicize party programs and as a means of protest. Became ubiquitous during the Cultural Revolution (q. V. ); guaranteed as one of the "four big rights" in the 1975 state constitution.