clapper-board

n (in film-making) pair of hinged boards brought together sharply to help in synchronizing the sound and the picture at the start of filming （拍电影时用的）拍板, 场记板.

clamorous, clamour (US clamor), clamp, clamp-down, clan, clandestine, clang, clanger, clangorous, clangour (US clangor), clank, clanking, clannish, clannishly, clannishness, clansman, clap, clap eyes on, clapboard, clapper, claptrap, claret, clarification, clarify, clarinet, clarinettist (also clarinetist), clarion, clarity, clash, clasp, clasp-knife, class, class-conscious, class-consciousness, class-feeling, class-list, class-mate, class-room, classic, classical,