People puzzled over them… until the internet found out what they were used for.
Some old doors have a small built-in hatch. Many people wonder what its purpose is.
This opening simply allowed one to speak to someone without fully opening the door. Before the invention of intercoms, this was a practical and reassuring way to identify a visitor.
- Numbered clothespins
One user noticed that each of his clothespins had a different number.
These numbers correspond to the molds used in industrial manufacturing. If a defect occurs in a batch of pliers, the manufacturer can quickly identify and replace the responsible mold.
- A strange device that was mounted near a door.
On some walls there is a small device with a hole and a miniature screen.
This is typically an alarm system installed near an outside door, for example, leading to the garden or swimming pool. It detects when the door is opened and triggers an audible alarm.
- A wooden ball covered with screws
- See more on the next page
