They are usually in such widths as to make them stock sizes for mortises.
That was not difficult, because the glue in the mortises had long since perished.
Lay out and cut the tenons and mortises for the end rails and back rail.
Score with the knife point the inner ends of the mortises of Y (n-o).
Mark plainly the parts to be cut out (the mortises), as on X in Fig. 250.