This was a type of candle alarm clock. Here’s how it worked:

• People would insert one or more nails or small metal objects into the side of a candle at different heights.

• As the candle burned down and reached the nail, the nail would fall onto a metal tray or holder, making a loud noise to wake the sleeper.

• Since candles burn at a fairly consistent rate (for example, one inch might take 20–30 minutes), people could estimate the time based on where the nail was placed.

📜 Historical context:

• This method was used from the 18th to early 19th century, especially in Europe.

• Some candles even had time markings to help with accuracy.