"Sunoko" is a Japanese wooden board made of slatted thick bars.
It is laid on the floor of a bathroom for preventing a person from slipping, and it is also used in oshiire (a built-in closet in a Japanese-style room) during the rainy season for preventing the goods in storage from molding.
These days, sunoko bed, which is futon (Japanese quilted bedding) laid on sunoko, is seen. There also exist other kinds of sunoko, including an aluminum version that is laid under a personal computer or a video game for promoting the cooling effect.
Wood absorbs moisture, so sunoko is convenient in humid places like Japan.