Burdock piling is a technique of Japanese wall building used to build castles, such as Osaka Castle

Osaka Castle

is a Japanese castle in Chūō-ku, Osaka, Japan.Originally called Ozakajō, it is one of Japan's most famous castles, and played a major role in the unification of Japan during the sixteenth century of the Azuchi-Momoyama period.-Description:...

 and named after the resemblance to the Japanese burdock

Burdock

Burdock is any of a group of biennial thistles in the genus Arctium, family Asteraceae. Native to the Old World, several species have been widely introduced worldwide....

 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 from their small size.

No mortar was used in the building of castle walls, which allowed the individual stones to move slightly during earthquake

Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

s without causing significant wall damage.

Another Japanese wall-building technique is known as disordered piling

Disordered piling

Disordered piling is a Japanese wall-building technique consisting of large number of small stones packed tightly together, used in some Japanese castle wall building. It would create a wall that was difficult to climb....

.