Chisel out the mortises taking care to keep the line d-e straight and square.

The ends (not the sides) of the mortises may be slightly undercut to insure a tight fit.
Fasten the other member, Y, upright in the vise so that the end to be tenoned will be flush with the top of the bench, and with the working face toward the bench.

Place on it the working face of X, (the member already dovetailed,) taking care that the inner ends of the mortises are in line with the working face of Y, and that the edges of the two members are in the same plane, as X on Y in Fig.250.Scribe with a knife point along the sides of the tails on the end of Y (f'-j' and g'-h').

Remove Y from the vise and square down these lines to the cross line l-m (j'-n and h'-o).

Score with the knife point the inner ends of the mortises of Y (n-o).