noun
koto bridge
The movable bridge of a koto (Japanese zither), used to adjust the pitch of each string.
琴柱を動かして調弦する。
Tune the koto by moving the bridges.
琴 refers to the koto instrument itself, while 琴柱 specifically denotes its bridges.
Compound of 琴 (koto, 'Japanese zither') and 柱 (ji, 'pillar, support'). The reading じ is a voiced form of し (柱).