When a newel post is made of a piece of wood, the giboshi is most often made of a metal, such as brass or bronze, in order to make the wood less susceptible to damage such as due to rain water.
親柱が木製の場合、擬宝珠は銅、青銅などの金属製である場合が多く、雨水などによる木材の腐食を抑える役目もある。