Nightingale floor
（重定向自Uguisubari）
Nightingale floors, or uguisubari (鴬張り) listen , were floors designed to make a chirping sound when walked upon. These floors were used in the hallways of some temples and palaces, the most famous example being Nijo Castle, in Kyoto, Japan. Dry boards naturally creak under pressure, but these floors were designed so that the flooring nails rubbed against a jacket or clamp, causing chirping noises. The squeaking floors were used as a security device, assuring that none could sneak through the corridors undetected.