sometimes doubled, Fig. 288, and a fillet (f) may be
inserted to cover the ends of the tenons, or the joint may be a blind
mortise-and-tenon, Fig. 266, No. 32, or in cheap construction, dowels
may be used. The best doors are now made with cores of pine covered
on the visible sides with heavy veneer. Large surfaces are covered
by increasing the number of parts rather than their size, as in
wainscoting.

Picture-frames also belong in this class of structures, the glass
taking the place of the panel. They are made with mortise-and-tenon
joints, Fig. 266, No. 33, slip joints, Fig. 267, No. 46, dowelled butt
joints, Fig. 264, No. 8, end lap joints, Fig. 265, No. 17, and, far
more commonly, mitered joints, Fig. 268, No. 52. Mitered joints are
the easiest to make, for the joints can be cut in a miter-box, Fig.
181, p. 104, and glued in a picture-frame-vise, Fig. 172, p. 101. This
joint needs reinforcement by nails, Fig. 268, No. 52, by dowels, No.
53, or by splines, No. 55. If the sides are of different widths, the
fitting of the joint is more difficult. Mitered joints are the only
kind suitable for molded frames. The rabbets are cut out with a
rabbeting-plane before mitering and assembling.

The principle disadvantage of a mitered joint is that, if the wood
shrinks at all, it opens at the inside corners, as in Fig. 289,
because wood shrinks sidewise but not lengthwise.

[Illustration: Fig. 289. The Way a Mitered Joint Opens on Account of
Shrinkage.]

In window sashes, the dovetail joint, Fig. 267, No. 47, is the common
one at the upper end of the lower sash and the lower end of the upper
sash, and the mortise-and-tenon joint modified is used at the lower
end of the lower and upper end of the upper sash. The glass takes
the place of the panel. In blind sashes, the pinned mortise-and-tenon
joint, Fig. 267, No. 38, is commonly used.

When panels are joined together to enclose a space, then we have what
is properly called cabinet construction. Illustrations are cabinets,
bureaus, desks, lockers, chests, etc.

In all these cases, the constructed panels may be treated as separate
boards and joined together with dowel pins or splines or dadoed
together without any other framework, tho the corners are often
reinforced by cleats or blocks glued into them. Sometimes, however, as
in chests, Fig. 290, posts are used instead of stiles, and rails are
mortised or doweled into them and the panels set into grooves in both
posts and r