The architect often furnishes the details of the window frame and of the sash, and generally the only important point in which they differ from the ordinary stock window frame, aside from the specially designed moldings, is in the sill, as at a, Fig. 42, and in a drip upon the bottom rail of the lower sash (b). The advantage is that water cannot drive under the sash, as it may in an ordinary window. If the water drives under the sash, it has access to the end wood of the stiles, and will in time cause them to decay.

Mullion frames, consisting of two or more windows in one frame, are frequently used. The mullion pulley stiles should be 3 1/2" or 4" apart, or far enough to allow the two sets of the window weights to work freely, if hung sash are used. A stud is frequently set in the mullion to support the header of the opening. If this is done it is plain that the backs of the mullion pulley stiles must be far enough apart to allow room for the stud and the two sets of weights. The header of the frame should extend the entire length between the end pulley stiles of the frame into which it should be grooved, the tops of the pulley stiles of the mullions being grooved into the underside of it.

Fig. 42. - Stool and Sash with Drip.

The pulleys for all window frames should be strong and stiff, for if made of too light metal, they will wear out quickly, or heavy weights may spring them, thus allowing the cord to catch, causing much trouble and annoyance. The top of the pulley is usually placed 5" from the under side of the header.

Frames for casement windows usually are made to allow the sash to swing out, as otherwise it is quite difficult to make them rain-proof. One objection to swinging the sash outward is that fly screens cannot be placed upon the outside of the window, though as they may be placed upon the inside, this is not a very important matter.

Window frames are often needed to accommodate center hung sash, which should swing with the lower half outward, otherwise the rain will be guided into the house. Sometimes sash are pivoted in the center of the top and bottom. This practice is not recommended for outside sash, as a rain-proof joint cannot well be made, though for inside work this method is quite satisfactory. A pin hinge is used for this, of which there are several forms upon the market.

38. Window sash. - The construction of window sash is practically the same in all parts of the country, though in some places the members are lighter than in others, thus making it necessary that the frame and the sash should be of different sizes for the same size of glass, according to the style of sash used.

The names of the different members of a sash are given in Fig. 43. If the sash springs out of shape, it is difficult and often impossible to make it run smoothly, besides causing such a strain upon the glass that a slight jar may break it; therefore only the best seasoned stock should be used.

A sash should be made as light as possible, in order that the weight may be at a minimum and that the glass surface may be at a maximum.

The strength of a sash depends upon its construction at the corners, which should be made in the strongest way possible. Figure 44 shows the mortised, tenoned, and coped joints of the top and bottom rails. The ends of the muntins are fastened to the rails by the same method. The tenon is split a little distance from the edge, as at b, or a saw cut is made by a thin saw, and a wedge (c) driven in, to make the tenon wider upon the outside of the stile than at the shoulder of the joint, thus forming a dovetail; the mortise is cut longer upon the ends to allow the split tenon to be pushed over. This should be done at each joint where a tenon comes through to the outside of the sash, though it is rarely done except upon the best work, or upon heavy sash. This is not the method in general use in the manufacture of common sash; commonly the tenons are pushed through, and the wedges driven between the ends of the mortise and the tenon. This gives fair satisfaction, and nearly all sash are made this way, as it is cheaper and easier. A hole is sometimes bored, and a pin driven through the mortise joint, and in large sash the joint is often draw-bored.

Fig. 43. - Sash Members.

The attention of the student is called to the joint between the meeting rails and the stiles (Fig. 45) as this has to stand hard usage. Most people in pushing up the bottom sash of a window lift under the middle of the top or meeting rail, and if the sash sticks a little, several heavy blows are usually given under it. In time, this will break the joint and destroy the sash; it may to some extent be prevented by using the strength as near the stiles as possible, working one side at a time, if the sash does not go up easily. To stand this usage the meeting rail is joined to the stiles by the dovetailed joint shown at aa, the strongest form of joint that can be used upon a sash of this sort.

A stronger form of sash than this is made, in which the stiles extend beyond the meeting rails about 3", as in Fig. 46.

Fig. 44. - Mortised and Coped Joint.

Fig. 45. - Meeting Rail Joint.

This form of sash should be used where the greatest strength is necessary.

The edges of the meeting rails which form the joint between the upper and the lower sash are joggled and beveled; they should fill closely the space between the upper and lower sashes, as at b, Fig. 45, occupied by the parting strip, which will be described later.

A 1" hole, 1" deep, should be bored about 14" from the top of the edge of each sash as at f, Fig. 43, and a 3/8" groove 1/2" deep cut from near the hole to the top of the sash, as shown at b, 6, leaving a space between its lower end and the hole, as shown at c. A 3/8" hole should be bored through c, from the groove to the hole, as shown at d, to allow a cord to pass through and to keep the knot in its place.

When the sash are in place, the joint between the meeting rails is made tight by means of a sash fast, which pulls them together.

39. Glazing sash. - - Glass should be cut about 1/8" smaller each way than the rabbet, to allow it to go in without forcing; it should be bedded before being laid in the rabbet. This is done by covering the part of the rabbet on which the glass rests with putty, as shown in Fig. 47, a. In order to do this successfully, the putty should be as soft as it can be handled, for the glass has to be pressed into it until it bears evenly, and only about 1/16" of putty is left between the glass and the wood, as at a. This pressure should

Fig. 46. - The Strongest Form of Meeting Rail Joint.

Fig. 47. - Secbe distributed lightly and evenly, therefore the necessity of soft putty. Another way of doing this, which is preferred by many workmen, is to roll a thin layer of soft putty upon a flat board; then by holding the glass at an angle, as shown in Fig. 48, a narrow strip of putty is taken off upon each edge as at a, and the glass laid in its place and carefully pressed down. This method can be applied only in a warm temperature, as the putty chills quickly. When conditions are right, it is the best and fastest way of bedding glass.