(fig. 13).

[Illustration: FIG. 11.--Bevelled Halving.]

[Illustration: FIG. 12.--Dovetailed Halving.]

[Illustration: FIG. 13.--Mortice and Tenon.]

[Illustration: FIG. 14.--Stub Tenon or Joggle.]

[Illustration: FIG. 15.--Dovetailed Tenon.]

[Illustration: FIG. 16.--Tusk Tenon.]

[Illustration: FIG. 17.---Bridle Joint.]

[Illustration: FIG. 18.--Foxtail Wedging.]

[Illustration: FIG. 19.--Dowelling.]

A stub tenon or joggle (fig. 14) is used for fixing a post to a sill; a
sinking is cut in the sill and a tenon is cut on the foot of the post to
fit into the sinking to keep the post from sliding.

The purpose of a dovetailed tenon (fig. 15) is to hold two pieces of
wood together with mortice and tenon so that it can be taken apart when
necessary. The tenon is cut dovetail shape, and a long mortice permits
the wide part of the tenon to go through, and it is secured with wood
wedges. Where the floor joists or rafters are trimmed round fires,
wells, &c., the tusk tenon joint (fig. 16) is used for securing the
trimmer joist. It is formed by cutting a tenon on the trimmer joist and
passing it through the side of the trimming joist and fixing it with a
wood key. Where large timbers are tusk tenoned together, the tenons do
not pass right through, but are cut in about 4 in. and spiked.

A bridle joint or birdsmouth (fig. 17) is formed by cutting one end of
timber either V shape or segmental, and morticing the centre of this
shaped end. Similar sinkings are cut on the adjoining timber to fit one
into the other; these are secured with pins and also various other forms
of fastenings. Foxtail wedging (fig. 18) is a method very similar to
mortice and tenon. But the tenon does not go through the full thickness
of the timber; and also on the end of the tenon are inserted two wedges,
so that when the tenon is driven home the wedges split it and wedge
tightly into the mortice. This joint is used mostly in joinery. The
mitre is a universal joint, used for connecting angles of timber as in
the case of picture frames. Built-up joints involve a system of lapping
and bolting and fishing, as in the case of temporary structures, for
large spans of centering for arches, and for derrick cranes. Dowels are
usually 3 or 4 in. long and driven into a circular hole in the foot of a
door frame or post; the other end is let into a hole in the sill (fig.
19).

[Illustration: FIG. 20.--Method of supporting Centering for Concrete.]

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