A steel bolt is a fastener having a head at one end and threads at the other, as shown in figure 6-85. Instead of threading into wood like a screw, it goes through a bored hole and is held by a nut. Stove bolts range in length from 3/8 to 4 in. and in body diameter from 1/8 to 3/8 in. Not especially strong, they are used only for fastening light pieces. CARRIAGE and MACHINE bolts are strong enough to fasten load-bearing members, such as trusses. In length, they range from 3/4 to 20 in.; in diameter, from 3/16 to 3/4 in. The carriage bolt has a square section below its head which embeds in the wood as the nut is set up, keeping the bolt from turning. An expansion bolt is used in conjunction with an expansion shield to provide anchorage in a position in which a threaded fastener alone is useless,

Driftpins (driftbolts) (fig. 6-86) are long, heavy, threadless bolts used to hold heavy pieces of timber together. Corrugated fasteners (fig.. 6-87) are used in a number of ways; for example, to fasten joints (miter) and splices together and as a substitute for nails where nails may split the timber.

Glue, one of the oldest materials for fastening, if applied properly, will form a joint that is stronger than the wood itself. Probably one of the best types of glue for joint work and furniture construction is animal glue, made from hides. Other types of glue are extracted from fish, vegetables, casein, plastic resin, and blood albumin. Glue can be obtained commercially in a variety of formsliquid, ground, chipped, flaked, powdered, or formed into sticks.

Figure 6-87.-Use of corrugated fasteners.