Толковый словарь английского языка Oxford English Reference - knocker

n. 1 a metal or wooden instrument hinged to a door for knocking to call attention. 2 a person or thing that knocks. 3 (in pl.) coarse sl. a woman's breasts. 4 a person who buys or sells door to door. Phrases and idioms knocker-up Brit. hist. a person employed to rouse early workers by knocking at their doors or windows. on the knocker 1 a (buying or selling) from door to door. b (obtained) on credit. 2 Austral. & NZ colloq. promptly. up to the knocker Brit. sl. in good condition; to perfection.