77. As examples of the species of working-drawings required for doors, we will give two specimens; the one from a building of modern architecture, and the other from a Gothic building.

Fig. 1, plate LV, is the elevation of an external door, with a light over it. It may either be made folding or to open in one, and framed to represent a folding-door. Fig. 2 shows half the plan of the door-way to double the size of the elevation; and, in practice, this plan is usually made of the full size of the parts. The lights over doors are now generally formed by metal bars.

78. When a door is framed to represent a folding-door, it is called a double-margined door. In framing a door of this kind, the middle stiles must appear to cross the top, lock, and bottom rails. Fig. 5, 6, and 7, show how this may be done; fig 5 is the double stile; fig 6 the side of the bottom rail; and fig. 7, the edge of the bottom rail with the double stile inserted. The joints are made to bevel a little, so that they may be perfectly close when the rail is driven to its place, but they should not be beveled more than is absolutely necessary for that purpose.

79. An elevation of an external door for a Gothic building is shown by fig. 3; and fig. 4 is the plan of the door and jamb to double the size of the elevation, in order to show the parts more distinctly. Doors of this kind are frequently ornamented by nail-heads along the mouldings; and lately such heads have been cast in iron; their peculiar form is shown in fig. 8; where A is the top of the head, and B its side, with part of the moulding. When the nail-heads are formed in wood, they are let in within the surface about a sixteenth of an inch.

Of Jib-Doors, Book-Doors, &c.

80. A JIB-DOOR is one intended to be concealed, either from its leading to a private room, or from there being no corresponding door, and it is therefore made flush with the surface of the wall, being generally canvassed and papered over, or painted the same as the room; the design being to conceal the door as much as possible, or to preserve the symmetry of the side of the room which it is in.

Fig. 1, plate LVI, represents the side of a room, in which KLMN is a jib-door, I the base moulding of the room, and H the surbase, both continued across the door.

Now, in order to make the jib-door open freely, the mouldings must be so cut that no point of the moving part may come in contact with the jamb of the fixed part. This may be done by forming the end of the moving part, and the end of the jamb or stationary part, in such a manner that all the horizontal sections may be circles described from the centre of the hinge. In short, by making the end of the base and surbase, and the edge of the jamb, the surface of a cylinder, of which the axis line of the hinges is the axis of the cylinder. This is shown by fig. 4, where A is part of the jamb; B represents a section of the door, upon which the iron containing the centre is fixed. C is the centre. The parallel lines in front represent the projections of the mouldings. Draw Cd perpendicular to the front line, and make de equal to Cd. from C, with the radius Ce, describe the circular line ef, and where the points of eC cut the parallel lines will be the extremities of the radii of the other circles.

Figure 2 exhibits the section of the surbase, marked H, in fig. 1; and B, fig. 3, is the elevation of the base, shown at I, fig. 1; and fig. 5 shows the section of the base moulding. 81. In libraries, concealed doors to private rooms or book-closets are frequently made to match the book-cases, and to appear as though the door was part of the book-case. For this