KOSHIDO (格子戸) is a door which has functions both separating and gain sunlight and air ventilation.
But on the other hand, KOSHIDO couldn't prevent cold air from outside in winter, so, it was developed as a paper sliding door (AKARI SHOJI 明障子）or a double lattice window (MUSOU KOSHI 無双格子).
Double lattice window (MUSOU KOSHI 無双格子) was invented to prevent cold air and avoid someone's eye but to gain sunlight in a room.
It consist of pair of KOSHIDO 格子戸. We can adjust the gap between wood bars by adjusting position of 2 doors. it makes a room more comfortable.
*MUSOU KOSHI 無双格子