sakakibashira 逆木柱

Also sakabashira 逆柱 or sakasabashira 逆さ柱. Lit. "upside down pillar."
1　An upside down spiral design applied to one of twelve pillars of on Nikkō Tōshōgū *Yōmeimon 日光東照宮陽明門 (1636) in Tochigi Prefecture. The other pillars are covered with white plaster with an all-over relief pattern called *guri 屈輪, a design that has double spirals. The sakabashira has the same design applied upside down.
2　An inverted pillar in a Japanese vernacular house. Throughout Japan, it was considered important that a vernacular house have an inverted pillar, one with the root end up and the top end down, to ward off ill luck for the occupants.