People used to tell the time with candles
In the era prior to the alarm clock’s invention, people had several methods to ensure that they got up in time. Most of these methods varied according to how people figured out what hour it was. Before mechanical methods for telling time became widespread, many used candles to know what hour of day or night it was.
Each marking represented a particular hour. If people ever needed to set an alarm, they would often put nails into the wax at the appropriate mark. As the day passed, the wax melted, and the pin eventually fell off, clattering onto the metal holder and alerting everyone in the house that time was up.