For people with power, being attacked by thieves or assassins in feudal Japan was not uncommon. Trained assassins were often difficult to spot since they had the knowledge and ability to pass the guards. In order to avoid getting surprised, feudal lords found a clever way to detect if their house was invaded by an attacking ninja: the nightingale floors.

Nightingale floors in English, or uguisubari in Japanese, were noise producing floors that served as an automated intruder alarm. The idea was simple: make creaky wooden floors that groan and screech with each step so you are alerted when someone enters your house. In fact, the name uguisubari literally translates to “bush warbler guard watch.”

Here’s how they worked. (the article continues after the ad)

Nightingale floors are basically planks of woods which are placed on a supporting framework. The planks are secured enough so they won’t move, but they are still loosely enough in order to slightly move when stepped on. And that’s what makes the magic happen: when someone walks on them their clamps rub against the nails that are attached to the beams thus creating a chirping noise:

And here’s a real picture of this “system”:

Nightingale floors can be found in historical seats of power, such as the Kyoto’s Nijo Castle which is a well known tourist destination for those visiting Kyoto. Here are some videos of people walking on these floors:

Of course, this bears the question: how did they know if the sound came from a trusted friend or an enemy? Simple. The lords would designate a walking rhythm. If they heard the sound at a different speed, they knew it was from a foe.

Brilliant.

If you like what you read, then you will definitely love this one: Why Are Asian Roofs Curved?

Photo: Kaigai no Bankoku Hannoki, Screenshot from archyev’s YouTube channel

Photoshop: I’m A Useless Info Junkie

Sources: Nightingale floors: The samurai intruder alarm system Japan’s had for centuries | The Nightingale floors: a Japanese flooring system which was used for catching intruders