A knocker-up (sometimes known as a knocker-upper) was a profession in England and Ireland that started during and lasted well into the Industrial Revolution and at least as late as the 1920s, before alarm clocks were affordable or reliable. A knocker-up's job was to rouse sleeping people so they could get to work on time.Photo source unknown, via British Paintings.
The knocker-up used a truncheon or short, heavy stick to knock on the clients' doors or a long and light stick, often made of bamboo, to reach windows on higher floors. At least one of them used a pea-shooter. In return, the knocker-up would be paid a few pence a week. The knocker-up would not leave a client's window until they were sure that the client had been awoken.
A knocker upper would also use a 'snuffer outer' as a tool to rouse the sleeping. This implement was used to put out gas lamps which were lit at dusk and then needed to be extinguished at dawn.