Figure 7.—Ranger Station, Lolo National Forest, Mont. Note the meticulous construction of box corners.
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Figure 8.—Framing the flat, or plain, tenon corner.
Nail a 1 inch by 1 inch cleat on the pattern board to points C and D and then make saw cuts on each end, cut chip off and smooth the surface. Turn log over and repeat on the other side. After framing out the sides of the tenon, the log is ready to be placed on the wall. Some fitting between corners is usually necessary but, if the logs are fairly straight and smooth, the work will be minimized.
The upright, or groove-and-tenon, corner ([fig. 9]) is used to a considerable extent in the West. It has desirable features from a mechanical standpoint: (1) The weight of the building is carried on the full length of the logs and does not rest solely on the corners, as in other types, and (2) it makes a tight wall because no openings will develop between the logs. Although not difficult to construct, the upright corner requires considerable mechanical skill and accuracy. A good carpenter can frame the entire building on the ground before any logs are placed on the foundation, after which it can be erected in a very short time. Next to the round-notch corner the upright, or groove-and-tenon corner, probably has the best appearance.