A knocker-up (sometimes known as a knocker-upper) was a profession in 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. 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. Pea shooters were also used. 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.
Knocker-up, Mary Smith, wielding a pea shooter, 1931.