pper side
without fail, Fig. 301, p. 199. The ends of flooring boards are also
slightly beveled so as to make a tight fit on the upper side.

7. _Select the simplest form of joint and use the smallest number of
abutments (bearing surfaces) possible, because the more complicated
the joint or the greater the number of bearing surfaces, the less
likelihood there is of a sound and inexpensive construction._

Illustrations of this principle are as follows: Usually a single
mortise-and-tenon joint is better than a double one because of
simplicity, strength and ease of making. Where much surface is
required for gluing, a double one may be better.

In a dovetail dado, Fig. 266, No. 28, p. 179, it is usually sufficient
to make the dovetail on one side only.

Many very elaborately spliced joints have been devised, which have no
practical advantage over the simple ones, Fig. 264, Nos. 4-7, p. 177.

A butt joint, Fig. 264, No. 11, is stronger than a mitered joint, Fig.
268, No. 52, in a box, for the latter is almost sure to shrink
apart. Where appearance is important, a ledge and miter joint has the
advantage of both, Fig. 268, No. 58.

8. _Keep a due proportion of strength between the fastenings (joints)
and the pieces fastened: i. e., the construction should neither be
frail on the one hand, because the pieces of wood are weakened by
too much cutting, nor clumsy, on the other hand, because then the
fastenings would be inordinately strong. In other words, the different
parts should be equally strong._

Illustrations of this principle are as follows: In a fished joint,
Fig. 264, No. 2, the plate should be attached so as to reinforce the
splice at the weakest point.

In a scarf joint, Fig. 264, Nos. 5 and 7, the angle should be oblique
enough to give the greatest leverage.

In a tusk tenon, Fig. 267, No. 40, the tenon is made but one-sixth the
thickness of the timber, whereas the tusk is made much larger.

Where a mortise is to be cut in a timber bearing weight, it should be
cut in the neutral axis, where the cutting of fibres will weaken it
least.

In the mortise-and-tenon of a table-rail, Fig. 267, No. 43, there
should be a wide shoulder above the tenon of the rail so that the top
of the leg above the mortise will not shear out. The mortise should be
as near the outside of the leg as possible so that the inner corner of
the leg may remain strong. The tenon should be strong enough to share
the strain with the shoulder