The movable frames which receive the glass in any style of window are called " sash," and are made in essentially the same manner throughout the country, and for various kinds of windows. Fig. 117 shows an elevation of the sash for a double-hung window and enlarged sections through the rails.

The pieces forming the top and bottom of the sashes are called "rails," and the side pieces are the "stiles." The small bars dividing the sash into lights are usually called "muntins," although sometimes called sash bars. The latter term, however, is more frequently applied to the bars which divide the large windows used in store fronts. The different pieces of glass are commonly called lights, and a window is spoken of as one-light, two-light, four-light, etc., according to the number of " panes" of glass in the whole window. Formerly windows of ordinary size were made with as many as eight and twelve lights, owing to the greater cost of large pieces of glass, but now such windows are generally made with only one light in each sash, which is called a "two-light window" when double hung. The sash in factory windows, etc., are still made with eight, twelve or eighteen lights, and small lights are sometimes used in dwellings for architectural effect. Glass is now so cheap, however, and it is so much easier to clean windows having but one light to each sash, that the large lights are generally preferred.

Fig. 116. - Detail of Bay Window..

As a rule, the size of a window is indicated by the size of the glass and the number of lights. Nearly all lumber dealers carry several sizes of sash in stock, already glazed, and such sashes are called

"stock sash." They cost a little less than custom-made sash, and are generally used in the cheaper class of buildings.

The common thicknesses of sash are 1 3/8-inch and 1 inch, but the former should only be used in the cheapest class of buildings. The usual proportions of the rails and stiles in such sash are given in Fig. 117. In New England the width A is generally only 1 inches and the width C only 2 inches, but in the Middle and Western States the dimensions given are almost universal.

In stock windows and in custom-made windows, unless otherwise indicated, the width, B, of the meeting rail is made 1 inch. In wide windows these rails are quite sure to spring, and should therefore either be made heavier or made of oak. The stiles are always made of the same section as the top rail.

Fig. 117.   Sash Details.

Fig. 117. - Sash Details.

Two details are shown for the meeting rail of the lower sash. Both appear to be commonly used, even in stock sash. In the 1 3/8 inch sash the lower meeting rail is shown rebated for the glass, and in the 1 -inch sash it is grooved to receive the glass. The former section contains the more wood, and hence is the stiffer of the two, but of course it offers greater obstruction to the vision. Occasionally the joint between the meeting rails is lapped, as shown by the dotted lines on the section of the 1 -inch sash, but this is not as desirable a joint as the straight bevel.

In all kinds of sash the rails are mortised and tenoned into the stiles, and the thickness of the tenon is usually' the width of the fillet T, shown in the sections. In thicker sash than those shown it should be about one-third of the thickness of the sash. The shape of the moulding on the inside of the sash may be varied to suit the individual taste, but should be of a shape that will permit of "coping" to advantage at the joints, the mouldings shown being about the best in this respect.

The weakest portion of a double-hung sash is the meeting rails and where they are tenoned to the stiles, and it is not infrequent that the tenon is pulled out of the mortise in raising or closing the window. To avoid this the stiles are sometimes extended below and above the meeting rails, as shown at X in the elevation drawing. This permits of making a strong joint, and is to be recommended for offices, tenements, etc. Such an extension, of course, prevents the sash from being raised or lowered its entire height, but in large windows this is of no great consequence.

Sash for plate or leaded glass should never be less than 1 inch thick, and 2 inches is to be preferred. For very large windows 2 -inch sash are sometimes used.

Single and double-strength glass is generally secured by tin "points" and putty. Plate glass is generally secured by a wood strip, as shown in Fig. 105.

Wooden sash should be made from the best quality of white pine, cypress or redwood, clear, straight-grained white pine being generally preferred. Hard wood sash are sometimes used, but they are more likely to warp than pine sash, and where a hard wood finish is desired it is best to veneer a pine sash.