It was a wall design to make a Shikkui (plaster) Okabe (whole surface of wall) look like a Shin-kabe (a type of plastered wall in which structural members are exposed) (structure) by having the shapes of pillars and Nageshi stand out on the Shikkui wall.
漆喰大壁を真壁(建築)に見せるために、柱や、長押を形のみ漆喰で浮かせた壁の意匠。