This method of joining timbers is sometimes used in heavy frame work, but can be used to advantage in light frame work that has to be taken apart, such as curtain frames, etc.
In [Fig. 74] is shown the assembled and the detailed drawings of this piece of work. The experience gained from the previous exercises can be used to advantage in working this problem.
The requirements in this exercise are that all pieces be square and to dimensions.
That the upright and cross-pieces when keyed be square to each other.
That the brace fit snugly, and form two angles of 45 degrees back at its junction with the upright and cross-piece.
That all joints fit closely, and the whole work be smoothed off and made true.
The method of laying out the keyed joint is somewhat similar to that in the third exercise.
Fig. 74.
On the upright locate the cross-piece (on the face edge), which is 1½ inches from the end to the upper edge, and measure the width of the piece, which is 1½ inches; draw the lines square to the face side, deduct the amount of splay or bevel that is given to the mortise and tenon from the lower end of the mortise, and add to the upper end the width of the key; draw the lines, and mark them in some manner so that they will be known as working lines. Figs. [75] and [76] will show how this may be done.