Pinning is the insertion of a pin of hard wood or iron through the timbers forming a joint, to prevent them from separating, or through a tenon, to keep it from drawing out of the mortise. In the latter case, the pin may be through the mortised beam, as shown in Fig. 176, or, if the tenon protrudes beyond the beam, the pin may be outside, as in Fig. 175, care being taken to have a sufficient length of tenon beyond the pin to prevent the end being shorn off by the pin if any strain comes upon it.

Pins should be made from pieces of hard wood, torn off from the baulk, in order that they may be of continuous fibre and uniform tenacity.

Drawboring is an arrangement for keeping the shoulders of the tenon quite tight up to the cheeks of the mortise, and for tightening pinned joints generally.

The pin-hole is first bored through the cheeks of the mortise. The tenon is then inserted, and the position of the hole marked upon it, after which it is withdrawn, and a hole bored in it a little nearer the shoulder. It is then again inserted, and an iron "draichore " pin forced in right through the holes, so as to bring the shoulder up as tight as possible. The drawbore pin is then removed, and the oak pin is inserted.

This operation is condemned by most writers, as it produces a constant and objectionable strain upon the pin and tenon; but it is nearly always resorted to in practice.

Nails

Different kinds of nails will be described in Tart III.

They are used for roughly and strongly connecting pieces of timber of moderate size, for securing boarding to beams, etc.

Spikes are large nails used for heavy work.

Trenails are pieces of hard wood used, like iron nails, for fastening boards to beams, for forming strong joints, etc., and occasionally, like pins, merely to secure joints formed in some other way.

They are useful in positions where iron nails would rust and injure the work, and where copper nails would be too expensive.

Trenails are generally of oak, cloven from the log, so that the longitudinal fibres may not be cut into.

They are from 3/8 to 3/4 inch in diameter, and from 3 to 6 inches long, according to the thickness of the pieces they unite, and slightly taper in form, to facilitate driving.