You will often have occasion to use this joint. The mortise is the hole in one of the two pieces to be joined. The tenon is the pin or projection in the other piece, shaped to fit the mortise.
Fig. 577.
Fig. 578.
Fig. 579.
To lay out a mortise and tenon (Fig. 577), select and mark the working faces for each piece. First take the piece in which the mortise is to be cut (Fig. 578). Square two lines, ab and cd, across the face and the same distance apart as the width of the piece on which the tenon is to be cut. Carry these lines across the side X (ae and cf) and also across the side opposite to X (that is, the side where the tenon will come through).
Next take the tenon-piece (Fig. 579) and measure from the end a distance a little greater than the width of the face of the mortise-piece, and at this point square a line, gh, across the face of the tenon-piece. Continue this line, gi, around the piece, with the square.
Now take the gauge and, setting it at the distance from the face settled upon for the mortise, scribe the line jk on the side X and also on the side opposite X. Also from the face of the tenon-piece, without changing the gauge, mark the line lm on the side X, on the opposite side, and on the end. Set the gauge to measure from the face to the other side of the mortise,—that is, add the width of the mortise to the figure at which the gauge was set,—and scribe another set of lines, op and rs, in the same manner as before, remembering to gauge all the time from the same face.