Papa ku'i is primarily made from wood, although in some cases you will find papa ku'i made from stone. The papa kuʻi ʻai (board) is used together with a pōhaku ku'i 'ai (stone pounder) in traditional food preparation.
Poho pōhaku or stone mortar was used together with the pōhaku kuʻi as the base to extract oil or grinds. It could also be used for the same purpose as we use cups today; for drinking, mixing dyes, lamps or chafing dishes.