Also written 真柱; called satsu 擦 or 刹. Lit. "heart pillar." The central pillar or shaft that forms the axis of a pagoda *tō 塔. It supports the spire *sōrin 相輪 that extends high above the roof. Originally, the shaft rested on a base stone *shinso 心礎, set deeply beneath the ground line. For example, the top of the base stone of Hōryūji *Gojū-no-tō 法隆寺五重塔 was found to be 3 m below ground level.
The earliest central pillars in the 7th century were formed from whole tree trunks stripped of bark, shaped and smoothed into an octagon. They were tapered and became roughly circular from the point where they rose beyond the roof. This shaping was necessary because various metal pieces were fitted to the central pillar to support the spire. The central pillar of Gojū-no-tō at Hōryūji reaches a height of 31.5 m with a diameter of 77.8 cm at its base. The diameter is 65.1 cm in the middle, and approximately 24.1 cm at the mid-point on the spire. Such huge pillars had to be divided into three sections: from the base stone to the third floor; from the fourth story to the point where the spire begins; and the spire section. The shaft of a three-storied pagoda *sanjū-no-tō 三重塔 is divided between the second and third stories, and again where the spire begins.
During the 8th century, shinbashira were erected on a base stone set at ground level. Example: Hokkiji Sajū-no-tō 法起寺三重塔 (742) in Nara. The use of this type of central pillar continued until the 13th century when it began to be positioned above the ceiling of the first floor, as found at Kaijūsenji Gojū-no-tō 海住山寺五重塔 (1214) in Kyoto. Very few examples of this method as used in five-storied pagodas between the 13th through 16th century remain. During the Edo period, the interior construction of a five-storied pagoda became more complex and the central pillar was suspended by chains. The bottom did not touch ground level but stopped a very short space above. Example: Nikkō Tōshōgū Gojū-no-tō 日光東照宮五重塔 (1818) in Tochigi Prefecture.