Burdock piling

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Burdock piling is a technique of Japanese wall building used to build castles, such as Osaka Castle and named after the resemblance to the Japanese burdock plant. Large rocks are fitted together over a mound of earth, and the remaining cracks are filled in with pebbles. This stone fill is called kuri ishi (i.e. 'chestnut stones') from their small size.

No mortar was used in the building of castle walls, which allowed the individual stones to move slightly during earthquakes without causing significant wall damage.

Another Japanese wall-building technique is known as disordered piling.