When a extraordinary ritual is conducted outside a shrine, this is the Invocation of the kami to be present at the ritual or to withdraw at its conclusion. This practice is from the time before the appearance of permanent shrine buildings, and was a necessary ceremony when a tree or boulder was chosen as the seat of the deity. Nowadays, the two practices are mainly used for ground purification rites (jichinsai) or roof-raising rites (jōtōsai). Procedures may vary slightly, but usually a table (an) is set up with a himorogi as the object in which the god is to be present (yorishiro). Then a priest (shinshoku) reads a norito, and makes keihitsu call to pray that the kami be present. This aspect of invoking the kami is called kōshin. When the rite is concluded, the keihitsu is again performed, and the kami are sent off. This is called shōshin.