truth window
n.β Β«A truth window is a common thing thatβs built into these rice straw buildings, because actually when they are covered with stucco itβs very difficult to tell, other than the very sort of soft look that the building has.Β» ββListener Builds Straw Bale Winery” by Frederica Churchill Living on Earth Nov. 29, 1996. (source: Double-Tongued Dictionary)