In writing this book the needs of carpenters and joiners who are studying the scientific principles of their work have been borne in mind throughout. Students who are attending classes at Technical Institutes to prepare for the examinations of the City and Guilds of London Institute in Carpentry and Joinery will find that the following chapters have the same aims as their syllabus, inasmuch as they are intended to develop an appreciation of general principles rather than to encourage empirical methods of work. In fact, the educational ideal underlying the syllabus of the City and Guilds of London Institute has constantly guided the author.

The simplest types of construction have been dealt with most fully, and the principles they embody have been emphasised continually. Without going into great detail, these rules have then been applied to more complicated examples; for a long experience has convinced the author that a student who has grasped the fundamental facts of a subject requires a minimum of guidance in more advanced work.

Unusual prominence has been given to the elementary parts of geometry, mensuration, and mechanics, because students of Carpentry and Joinery constantly begin their work without this necessary preliminary knowledge. Among other special features of the book are the chapters on tools and woodworking machinery as well as the large number of pictorial diagrams of details of construction.

It is hoped that in addition to its use by students of technical classes the book will be of service to practical men in the workshop and to schoolmasters framing courses of manual training.

Summaries are given at the ends of the chapters, and ample material for testing the knowledge of the student will be found in the questions - chiefly derived from past examination papers of the City and Guilds of London Institute - which immediately follow the summaries.

Size and Position. - The sizes and positions of window openings are influenced by the size of the rooms, and the purposes for which the building is used. For the sake of ventilation, and also to secure good lighting, the windows should be placed at as great a height as the construction of the room will allow. In dwelling-houses the height of the sill is usually about 2' 6" above the inside floor level.

Construction. - The framework holding the glass of the window may be fixed or movable. It must be so prepared that the glass can be replaced easily when necessary. In ware- houses, workshops, and similar buildings, the frames holding the glass are often fixed as fast sheets (Fig. 734). As however, this arrangement affords no means of ventilation, it is more usual to have the glass fixed in lighter frames called sashes. If the sashes are hung to solid rebated frames, and open as doors do, the windows are called casement sashes. If they slide vertically and are balanced by weights or by each other, the window is a sash and frame window. Other methods of arranging sashes, either hinged, pivoted, or made to slide past each other, are described in detail later.

Sashes. - The terms used for the various parts of sashes and fast sheets are somewhat similar to those employed in describing doors. Thus, the styles are the outer uprights, and the rails are the main horizontal cross-pieces: top rails, meeting rails, and bottom rails being distinguished. Any intermediate members, whether vertical or horizontal, are named bars.

Sashes are from 1 1/2 to 3 inches thick. The inner edge of the outer face is rebated to receive the glass. The inner face is left either square, chamfered, or moulded; two common forms of moulding are lambs-tongue (Fig. 736) and ovolo (Fig. 737).

The size of the rebate is indicated in Fig. 735; it varies with the thickness of the sash, its depth being always a little more than one-third this thickness. The width of the rebate varies from a quarter of an inch to half an inch, and the mould is usually sunk the same depth as the rebate. This last fact is of some importance, as it affects the shoulder lines; and with hand work it influences the amount of labour in the making of the sashes.

Ah little material as possible is used in the sashes, in order that the light shall not be interfered with. In general, the styles and top rail are square in section before being rebated and moulded. In casement sashes, however, it is often advisable to have the outer styles a little wider than the thickness, especially when they are tongued into the frame. The width of the bottom rail is from one and a half to twice the thickness of the sash. Sash bars, which require rebating and moulding on both sides, should be as narrow as possible, in order not to interrupt the light. They are usually from five-eighths of an inch to one and a quarter inches wide.

Joints of Sashes. - The sashes are framed together by means of the mortise and tenon Joint (Fig. 739). The remarks made on p. 348 respecting the proportions of the thickness and width of tenons, haunched tenons, etc., are to a large extent applicable here also. Hardwood cross-tongues are sometimes inserted to strengthen the joints (Fig. 302), while thick sashes should have double tenona {Fig. 782). The best joint for connecting sash bars is shown in Fig. 740; this method is known as halving. An alternative to halving in sash bars is to arrange that the bar which is subjected to the greater stress - as for example, the vertical bars in sliding sashes, and the horizontal bars in hinged casement sashes - shall be continuous; this continuous bar is mortised to receive the other, which is scribed, i.e., cut to fit the first, and on which the short tenons are left. This method is called franking the awn bars, and is illustrated in Fig. 741.

Casement Windows. - Casement windows may be hinged in such a manner that they open either inwards or outwards. They may consist either of one sash, or of folding sashes, and are hung with butt hinges to solid rebated frames. These frames consist of jambs, head, and sill. The head and sill "run through," and are mortised near the ends to receive tenons formed on the ends of the jambs. The upper surface of the sill is weathered to throw off rain water. Casement windows which reach to the floor are usually called French casements. Their sashes require an extra depth of bottom rail.

Casement Sashes opening Inwards. - Figs. 742 to 745 show the elevation and vertical and horizontal sections, of a window opening in a 14" brick wall fitted with a casement window having folding sashes to open inwards. In this class of window the frame is rebated for the sashes on the inner side. Each sash has, on the outer edge of the outer style, a semi- circular tongue, which fits into a corresponding groove in the jamb of the frame. This tongue renders the vertical joint between the sash and frame more likely to be weather proof; it is to provide for the tongue that the extra width of style already referred to is necessary. The tongue, however, is often omitted, as in Fig. 746. It will be seen readily that, if the sash were in one width, it would be impossible to have a tongue on more than one edge of it. With easement sashes opening inwards, the greatest difficulty is found, however, in making a water-tight joint between the bottom rail of the Bash and the sill of the frame. Figs. 746 and 747 show two methods by which this may be accomplished feature of all these sashes is a small groove or throating on the under edge of the bottom rail; this prevents the water from getting through. The groove in the rebate of the sill (Fig. 747) is provided to collect any water that may drive through the joint. This water escapes through the hole bored in the centre of the sill.

When casement sashes are hung after the manner of folding doors, the vertical joint between the meeting styles is rebated. Alternative methods of rebating are shown in Figs. 748 and 749. Fig. 749 is known as a hook joint and is the better one.

Casement Sashes opening Outwards. - These are more easily made weather proof than inward-opening sashes. The chief objections to their adoption are that they are not easily accessible for cleaning the outside, especially in upper rooms, and that they are also liable, when left open, to be damaged by high winds and to let in the rain during a storm. Fig. 750 is a sketch of one corner of such a window. It will be noticed that these frames, like door frames, have the exposed arrises moulded in various ways, and that the sashes may either be hung flush with one face of the frame, as in Figs. 745 and 746, or fit in the thickness of the frame (Figs. 747 and 750). The sill in Fig. 749 is shown to be double sunk, i.e. to have the upper surface - upon which the bottom rail of the sash fits - rebated with two slopes (weatherings).

Other Hinged Sashes. - Various different methods of arranging - in solid rebated frames - sashes which can be opened for purposes of ventilation, etc., though they may be in positions difficult of access, are shown in Figs. 751 to 754. Fig. 751 is the elevation of a window, the lower sash of which is fixed in the frame, the upper sash being hinged on the bottom rail to open inwards. The bottom rail is rebated to fit the transom (the intermediate horizontal member of the window frame); the upper side of the transom is weathered and double sunk, as shown in enlarged section (Fig. 752). Such an arrangement is also applicable to a fanlight over a door, where the sash may be made conveniently to fit into the rebate of the door-frame. Fig. 754 is a section through a similar window with the sash hung on the top rail. A sash so hung must of necessity open outwards, to keep out the rain, etc.