Hakushu (拍手 (神道))
The term "hakushu" or "kashiwade" (both of which mean clapping) refers to a gesture people make when they offer prayers to gods (deities, spirits) at Shinto religious services or before Shinto shrines or household altars. Hakushu is written with the Chinese characters for 'beat' and 'hand' (拍手) or 'oak hand' (柏手) and it is also known as "hirate" (開手 - 'open hand').
Ｅtiｑuette
Join your palms, and after spreading your hands to the sides, join them again. Generally, clap your hands when rejoining your palms to make a sound. Since the purpose of making clapping sounds is to express gratitude or joy, the etiquette is different at solemn events and when expressing sorrows (see below). It is also said that the clapping sounds are made to invoke gods to make your wish come true or to ward off evil spirits. In this sense, making silent hakushu can be construed as avoiding warding off spirits of the dead.
Types
There are several types of hakushu. One type is the 'mijikate' (short claps) of three or less hand claps, such as the 'nihai-nihakushu-ippai' (The greeting of Shintoism which performs a bow twice first, then applauds twice, and finally bows once) generally employed when people visit shrines today. Four or more hand claps, such as those used at Izumo-taisha Shrine (four claps), Usa-jingu Shrine (four claps) and Ise-jingu Shrine (eight claps) are known as 'nagate' (long claps). There is another type called 'yahirate', which is eight claps followed by a final short one. Among other types are 'shinobite' (soundless clapping), in which hands are clapped silently at Shinto funerals, and 'raishu', one clap made when receiving a cup of sake at naorai (banquets held at the end of festivals).
More specific examples of hakushu etiquette include occasions when the palms are joined exactly so that the tips of the fingers (including the thumb) meet the tips of the same fingers of the other hand and occasions when the palms are intentionally not joined so exactly. The latter case is further divided between times when the palms are joined exactly at first and then slid half way through; and another time when the palms are not precisely joined from beginning to end.
Reasons for not aligning the palms exactly include 'to make a clearer sound' and 'to avoid contact between the clean hand and the unclean hand', and also depend on religions and sects (e.g. Shintoism or Buddhism, court nobles or warrior households).
For a clearer sound, claps are made such that the tips of the fingers of the right hand go between the fingers of the left hand.
Origin
From the description of "People clapping their hands to show respect to others"in the Gishi-wajin-den (the first written record of Japan's commerce) of handclapping as the customary greeting of the people of Wa (the Japanese) in the Yamatai-koku Kingdom, used in veneration of nobles, it is understood that hakushu was also made toward people in those days. This shows that hakushu were made toward both gods and nobles in ancient times but the custom of hakushu toward humans gradually died out, leaving only the practice of hakushu toward gods.
Another study suggests that ancient people clapped hands in greeting others for the purpose of expressing their respects and showing that they neither had weapons in their hands nor felt hostility,
According to a popular theory, the name 'kashiwade' comes from mistaking '拍' (pronounced as 'haku') for '柏' (pronounced as 'haku' or 'kashiwa') or from confusion between the two similar characters. Another theory relates it to 'kashiwade', which means a court cook. There is still another theory that the shape of the joined hands was likened to an oak ("kashiwa" in Japanese) leaf.