The commonest type of window for the small house is equipped with the double-hung sash. This sash should be made of 1⅛-inch white pine, mortised and tenoned at the corners. The meeting rail ought to be rabbeted so that water is prevented from seeping through, and the bottom rail ought also to be rabbeted to fit over a similar rabbet in the sill. The size of the lower rail is usually 3 inches wide, the sides and top rails 2 inches wide, and the meeting rail 1⅛ inches wide. It is generally admitted that a window has little architectural charm without muntins, and these are made ¾ inch wide, as a rule. The glass of the window is inserted into the sash frame at least ¼ inch, and its plane is about one-third in from the outside face of the rails. The over-all dimensions of a window sash are determined by the size glass used, and as glass is cut in inches, the over-all dimensions of a sash will be in fraction of inches. For example, a double-hung sash of twelve lights, each 8 inches by 10 inches, will give a sash opening of 2 feet 4½ inches by 3 feet. If the lights measure 9 inches by 12 inches, then the sash size will be 2 feet 7½ inches by 4 feet 6 inches. [Illustration] The best type of double-hung window-frame is constructed so that the blind stop is rabbeted to receive the pulley stile, preventing any wind from blowing through. The pulley stiles are usually made of yellow pine, but the outside casing and sills should be of white pine. It is also a good precaution to have the sill rabbeted to receive the ground strip, so that air cannot come underneath the sill. The use of 1³/₁₆ inch-thick material is common for all parts of the frame except the sill, which ought to be 1¾ inches thick. A 2¼-inch depth should be allowed for the weights in the box, and a space of ⅞ inch left between the stud and the top of the frame. Parting strips are made ⅜ inch wide. Where the frame is to be built into a masonry wall, the back of the weight-box is closed in, and a moulding, called the brick mould, should be provided for covering the outside joint between frame and masonry. In order to make this joint tight in hollow-tile construction, it is essential to stuff the back of the brick mould with elastic roofing cement. [Illustration: CASEMENT WINDOWS]