coping; top rail
In architecture, the protective cap or top rail on a wall, fence, or balustrade.
top part of the upper cross-beam of a torii
Specifically the uppermost horizontal beam of a Shinto torii gate.
The coping on the wall has deteriorated, so it needs to be replaced.
The top beam of a torii often has a curve.
Compound of 笠 (kasa, “conical hat; umbrella-like cover”) + 木 (ki, “wood”), referring to a wooden cap or covering piece.