How did knocker-uppers know what time to wake people up?
Frequently Asked Question about the extinct profession: Knocker-Upper
Knocker-uppers were hired individuals in the 19th and early 20th century who were responsible for waking people up in the morning before the invention of alarm clocks. They would often use long sticks to tap on windows or doors to wake up their clients. They would know what time to wake people up by memorizing their schedules or by using their own personal timekeeping devices, such as a pocket watch or sundial.