A hollowed out wooden coffin is called a "Sakitake-shiki mokkan" (split bamboo type wooden coffin) and made of a big tree which is divided into two pieces; the inside of both pieces is then hollowed out and became a cover and body of the coffin.
木棺のうち刳りぬき式のものは、巨木を縦に二つに割って、それぞれ内部を刳りぬき、蓋と身とが作られたものと考えられ、「割竹式木棺」と呼び習わされている。