Fig. 217a. A covered seat (continued)
In any work of this character, two boys should work together, and two trestles or saw horses will be a necessary part of their equipment. In mortise and tenon joints of this character a method called draw boring is frequently used. (See b, [Fig. 217b].)
The hole for the pin or dowel is first bored across the centre of the mortise. The tenon is inserted snugly, and the bit again inserted until it makes a mark on the tenon. The tenon is withdrawn, and the centre of bit placed 1⁄16 inch nearer the shoulder than the mark made, and the hole bored. This brings the distance y slightly less than x.
The three holes through which the pin is to pass are not in line when the tenon is again placed in mortise. The result is to draw the tenon tight, when the pin is driven home, and to make the joint a very snug one, as it should be.
Fig. 217b. Draw boring a joint and method of levelling posts
If this method of constructing the frame on the ground is not used, the tie piece must be placed in position before the second post is set. Fasten the joints with the pins, and level the tie piece. If the two posts have been laid out together on the trestles, their tops must now come level and true.