The construction of doors is essentially the same, whether they are to be used as outside or as inside doors, the only difference being in the thickness of the door and in the finishing of it. The most simple kind of door is, of course, a single piece of board, with hinges at the side, but this is almost never satisfactory for any purpose, as it is likely to warp, crack, and shrink, and has not sufficient strength. It is customary in every case to build up a frame of comparatively heavy pieces and then to cover it over or to fill it in with lighter stuff in the form of panels. In such a framework for a door, the vertical pieces are called stiles, and the horizontal pieces are called rails. There are always at least two stiles and at least two rails, a stile at each side of the door, and a rail at top and bottom, but there may be more than two of each of these members. The stiles usually extend the full height of the door, from top to bottom, and the rails are tenoned into them. As mentioned above, the number of rails may be varied to suit the conditions, or the taste of the designer, so that the door will have many small panels, or a few larger ones. After the frame has been built up in this way, the door may be finished as desired, that is, with sunk panels in the spaces between the rails and stiles, or with the framework covered with sheathing on one or both sides so as to present a plain surface without panels. Most of the simple, heavy doors for use in inconspicuous positions, such as doors for barns and outhouses, gates on walls, etc., are made with only one side covered with sheathing fastened to a rough frame.

The sheathing is sometimes put on vertically or horizontally, but a much stronger door is obtained if it is put on diagonally. It is possible, indeed, to make a satisfactory door by the use of sheathing alone, without any frame. The sheathing is put together in two thicknesses, and diagonally, but each thickness is made diagonal in the opposite direction to the other thickness so that all the pieces cross each other. Such a door is shown in Fig. 347. In Fig. 348 is shown a door with diagonal sheathing on the outside of a framework. Fig. 349 shows a strong type of door with a braced frame which is covered on one or both sides with vertical sheathing.

Fig. 347. Double-Diagonal Door Sheathing.

Fig. 348. Diagonal Sheathing on Door Frame.

Fig. 349. Braced Door Frame with Vertical Sheathing.

There is no difficulty in fastening together the simple doors just described, but when we come to the paneled doors, there are some special methods in use for fastening the rails into the stiles at the corners, which must be described. There are also special ways of building up the members of which the doors are composed, to prevent warping and twisting.

In Fig. 350 is shown the most simple type of door for use in the interior of a building. It is called a "four-panel" door on account of the arrangement of the panels and their number. The stiles, marked A in the figure, are all made not less than 4 1/2 inches in width. The middle rail, marked B, is made 8 inches wide, and the top rail C the same as the stiles. The bottom rail, marked D, is made wider also, its width being about 10 inches. The panels are marked EE.

Figs. 351 and 352 show other arrangements of panels which may be employed, but the sizes are all the same as in Fig. 350. Of course, the more cross rails there are between the top rail and the bottom rail, the stronger will be the door.

The point of greatest interest in the construction of a door is the joint between the top rail C and the stiles AA. The rail is always tenoned into the stiles, the stiles continuing all the way up to the top edge of the door, and this joint is never made as a mitered joint. Fig. 353 shows the tenon by dotted lines.

Fig. 350. Four-Panel Door.

Fig. 351. Door with Horizontal Panels.

Fig. 352. Another Form of Door Paneling.

It will be seen that it does not go all the way through the stile of the door but should be stopped back about 1/2 inch, so as not to show on the edge of the door.

Fig. 354 shows how a door should be constructed, the figure being a section taken through the stile of the door. The entire piece is built up out of strips of pine § inch thick, and of a width equal to the thickness of the door, minus 1/2 inch for a veneering of 1/4 inch thick on each side of the door. These strips are carefully glued together, side by side, thus forming the finished piece on which the veneering is applied. Fig. 354 also shows the proper construction of a panel at the place where it joins the stile or the rail.

A piece marked A in the figure is first glued into the stile or rail, and to this are glued the panel moldings, after the panel has been put in place, the panel moldings projecting out beyond the piece A far enough to hold the panel, which is thus left free to move as it shrinks or swells. The panel will remain as a plain surface, and will not bulge or crack. The moldings should never be fastened in any way to the panel itself. Unless the panel is absolutely free to move it is sure to crack badly,

Fig. 353. Construction of Joints between Top Rail and Door Stile.

Fig. 354. Section Showing Panel Construction.