A style of window in a folk house. The opening and closing of the window sash moves along a certain horizontal direction, so it is called "casement window". Flip window and sliding window two kinds. There are multiple single Windows, which turn upward when opened and are fixed by the iron rod support on the window frame; Some also turn down and open to a certain extent to hold the chain on the window frame. Push and pull more than two Windows. When opening and closing, the window sash slides horizontally along the slot of the window frame, or slides up and down. The front window of the houses in the northern Siheyuan is mostly turned over. The center of the window is inlaid with wooden mullion and pasted with white paper. When the window is opened, it turns outward. In the south, it is also common to flip Windows in the attic and ceiling.