Majority of mokkanbo was called kumiaishiki (unit style), which were generally made by combining six boards, a bottom board, two side boards, two end boards, and a lid board, and the coffin was placed inside a dug out hole.
弥生時代の木棺墓の大半は組合式と呼ばれるもので、一般的には、底板・両側板・両小口板・蓋板の計6枚の板材を組み合わせ、あらかじめ掘削された土坑の中に棺を作るものである。