outer ribs of a folding fan
Refers to the two thick ribs at each end of a folding fan. A specialized term used in contexts related to traditional fans.
扇子の親骨が折れてしまった。
The outer rib of the folding fan broke.
outer frame of a lattice door
Refers to the outer frame of a lattice door (格子戸). A specialized architectural term.
古い家の格子戸の親骨が傷んでいる。
The outer frame of the lattice door in the old house is damaged.
Compound of 親 (oya, 'parent; main') and 骨 (hone, 'bone; frame'), literally 'parent bone'. The term refers to the main structural rib or frame in fans and lattice doors.