The flat, or plain, tenon corner ([fig. 8]), is also common. It may be made in two ways. In one, only the bearing surfaces are framed, while in the other, all four sides of the tenon are framed flat. The plain tenon corner does not have the highly desirable feature of being self-locking. However, it is simple to make and economical, and therefore especially suitable for temporary structures. The logs must be pinned together, as shown in [figure 11]. All the framing can be done on the ground, before the logs are put in place. Carefully fitted, this makes a neat-looking job.
Directions for constructing the flat, or plain, tenon corner.—Square one end of log, as in [figure 8], at point A, then measure required length and saw the opposite end square, at B. If the log has any curvature, turn it on the skids until its back is up. Determine the thickness of the tenons, based upon the average top and butt diameters of the log. Then take an 18-inch length of board the same width as the thickness of the tenons, driving a nail through its center and into the center of the log. Place the spirit level on top of the board and mark lines on the log at the top and bottom edges. The width of a tenon varies with the diameter of the logs; 8- to 10-inch diameters will produce 6- to 7-inch wide tenons.
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Figure 6.—Marking and framing the dovetail, or box, corner.