241. Pins are employed principally as a means of holding tenons in mortises. In carpentry one pin, generally, is used in each joint, its diameter varying from one-sixth to one-fourth the width of the tenon. It is commonly placed at a distance from the abutting cheeks of the mortise, equal to one-third the length of the tenon. But to secure the maximum strength of the joint, its exact location in any particular case must be fixed with reference to the character of the material, and also to the relative thickness of the tenon and the cheeks of the mortise. In joinery it is found best to use two or more pins, and, whatever the proportions of the joint may be, these rarely exceed three-eighths of an inch in diameter. They are inserted very near the abutting cheeks of the mortise, so that that part of the mortise between them and the shoulder of the tenon will not shrink enough to make an open joint.

Square pins are better than round ones, but the latter are more easily fitted and, therefore, more used. Drawboring has already been described (168).