A Knocker-upper, was a profession in Britain and Ireland that started during and lasted well into the Industrial Revolution, when alarm clocks were neither cheap nor reliable, and to as late as the beginning of the 1920s. A knocker-up’s job was to rouse sleeping people so they could get to work on time.
The knocker-up used a baton 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.
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.
There were large numbers of people carrying out the job, especially in larger industrial towns such as Manchester. Generally the job was done by elderly men and women but sometimes police constables supplemented their pay by performing the task during early morning patrols.
source: wikipedia