An Usu is a large Japanese mortar

Mortar and pestle

A mortar and pestle is a tool used to crush, grind, and mix solid substances . The pestle is a heavy bat-shaped object, the end of which is used for crushing and grinding. The mortar is a bowl, typically made of hard wood, ceramic or stone...

 with a pestle called kine (ˈkinɛ̝), used to pound rice

Rice

Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 or millet

Millet

The millets are a group of small-seeded species of cereal crops or grains, widely grown around the world for food and fodder. They do not form a taxonomic group, but rather a functional or agronomic one. Their essential similarities are that they are small-seeded grasses grown in difficult...

.

While the function of an usu is similar to the smaller suribachi

Suribachi

Suribachi and surikogi are a Japanese mortar and pestle. These mortars are used in Japanese cooking to crush different ingredients such as sesame seeds....

and surikogi mortars, the shape is very different, as the usu usually lacks the rough pattern in the bowl

Bowl (vessel)

A bowl is a common open-top container used in many cultures to serve food, and is also used for drinking and storing other items. They are typically small and shallow, although some, such as punch bowls and salad bowls, are larger and often intended to serve many people.Bowls have existed for...

, and has a differently shaped pestle which is used in a different manner.

Appearance

The usu is usually about one meter high (including pedestal) and has a diameter of ca. 30 cm. The usu is usually comprises wood or stone. The kine is a long wooden mallet

Mallet

A mallet is a kind of hammer, usually of rubber,or sometimes wood smaller than a maul or beetle and usually with a relatively large head.-Tools:Tool mallets come in different types, the most common of which are:...

 with a length exceeding one meter. The usu is usually operated by two people at the same time. One person swings the kine to pound the rice in a similar motion to chopping wood. It is physically demanding work and is usually done by men who often chant

Chant

Chant is the rhythmic speaking or singing of words or sounds, often primarily on one or two pitches called reciting tones. Chants may range from a simple melody involving a limited set of notes to highly complex musical structures Chant (from French chanter) is the rhythmic speaking or singing...

 to keep time. Between each swing, another person puts his hand in the bowl to turn the rice. Timing is critical for safe operation of the usu.

Use

The most common use of an usu is to pound cooked white rice into a very sticky mass in order to produce mochi. It is still frequently used in Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

in traditional restaurants and also sometimes in traditional, rural, or wealthier private households. It is claimed that mochi pounded in an usu and kine tastes better than mochi that has been processed by an electric machine.