ul to measure from the centre
of the spar, as it may be set at an angle, and the rear of it may be
considerably lower than its front.

BORING HOLES IN WOOD.--It should be a strict rule that no spar be used
which has an unnecessary hole in it. Before boring a hole, its position
should be confirmed by whoever is in charge of the workshop. A bolt-hole
should be of a size to enable the bolt to be pushed in, or, at any rate,
not more than gently tapped in. Bolts should not be hammered in, as that
may split the spar. On the other hand, a bolt should not be slack in its
hole, as, in such a case, it may work sideways and split the spar, not
to speak of throwing out of adjustment the wires leading from the lug
or socket under the bolt-head.

WASHERS.--Under the bolt-head, and also under the nut, a washer must be
placed--a very large washer compared with the size which would be used
in all-metal construction. This is to disperse the stress over a large
area; otherwise the washer may be pulled into the wood and weaken it,
besides possibly throwing out of adjustment the wires attached to the
bolt or the fitting it is holding to the spar.

LOCKING.--Now as regards locking the bolts. If split pins are used,
be sure to see that they are used in such a way that the nut cannot
possibly unscrew at all. The split pin should be passed through the bolt
as near as possible to the nut. It should not be passed through both nut
and bolt.

If it is locked by burring over the edge of the bolt, do not use a heavy
hammer and try to spread the whole head of the bolt. That might damage
the woodwork inside the fabric-covered surface. Use a small, light
hammer, and gently tap round the edge of the bolt until it is burred
over.

TURNBUCKLES.--A turnbuckle is composed of a central barrel into each end
of which is screwed an eye-bolt. Wires are taken from the eyes of the
eye-bolt, and so, by turning the barrel, they can be adjusted to their
proper tension. Eye-bolts must be a good fit in the barrel; that is to
say, not slack and not very tight. Theoretically it is not necessary
to screw the eye-bolt into the barrel for a distance greater than the
diameter of the bolt, but, in practice, it is better to screw it in
for a considerably greater distance than that if a reasonable degree
of safety is to be secured.

Now about turning the barrel to secure the right adjustment. The barrel
looks solid, but, as a matter of fact, it is hollow and much more fra