Joint.]

In the case of the scarfed joint at Fig. 218 (used for purlins) the
length of the scarf is usually made about four times that of the depth of
tie beam. It has two hardwood keys which force the pieces together and
thus tighten the joint.

[Illustration: Fig. 218.--Detail of Scarfed Joint in Purlins.]

The methods of scarfing and fish-jointing are many and varied, and, in
selecting a joint, the nature of the pieces to be joined and the
direction and the amount of the load should be carefully taken into
consideration.

The above joints come under the heading of carpentry, and the ordinary
tools such as the saw, plane, boring-bit and chisels are all that are
requisite and necessary to produce a sound and serviceable joint. Scarfed
joints are generally of large size, and they are usually made by placing
the work upon sawing trestles owing to the bench being too small to
accommodate the large timbers.

[Illustration: Fig. 219.--Example of Tabled Joint with Straps.]

[Illustration: Fig. 220.--Lapped Scarf Joint with Bolts for Heavy
Timber.]

Fig. 219 is a tabled scarf joint which admirably resists tension and
compression. It is very easy to make and fit, and is not materially
affected by shrinkage. The rectangular wrought iron straps are knocked up
over the joint after the two pieces engage. The length of the joint
should be approximately five times its thickness.

Fig. 220 is an example of a lapped scarf joint which is secured with nuts
and bolts. It effectively resists compressional stress in vertical posts
and it may, if required, be strengthened by the addition of wrought iron
fish plates. It is quite a serviceable joint for all general purposes,
such as shed or garage building where fairly heavy timbers are used.

THE HINGED JOINT

One of the most common forms of hinged joint in use to-day is that formed
by using the "butt" hinge, and many troubles experienced by the amateur,
such as "hinge-bound," "stop-bound," and "screw-bound" doors, etc., are
due to a lack of knowledge of the principles of hingeing. Hinges call for
careful gauging and accurate fitting, otherwise trouble is certain to
occur.

A "BOUND" door or box lid is said to be hinge-bound when the recess which
contains the hinge is cut too deep. The frame and the body portion engage
too tightly when closed, the result being that the door has always a
tendency to open a little. This fault may be in many cases remedied by
packing behin