The tenon is not necessarily cut back from the inside, unless a groove for a panel is made in the inner edges of the styles and rails. In this case the inner edge of the tenon is made level with the bottom of the groove, the depth of which latter may also determine the projection of the part S from the shoulder.

If the frame is not to be fitted with a panel, the groove will probably not be required, and the inner edges of the tenons may be made level with the inside edges of the rails. The lines which were scribed on the styles to indicate the internal length of the frame will also serve to mark the inner ends of the mortises, the outer ends being marked by similar lines, which are made as much beyond the first as the width of the intended tenons. If a groove be necessary, the lines determining the length of the styles will not be correct for the inner ends of the mortise; consequently new lines must be marked in advance, the intervening space being equal to the depth of the groove.

The frame represented in figs. 79 and 80 is furnished with a panel, and the groove to receive it is shown by the dotted lines g, g, in fig. 79. The width of the the tenons, which varies from about one-half to two-thirds that of the rail, being determined upon, it is now necessary to mark out the mortises in the manner already described, and at once proceed to form these parts and put the frame together.

In joining, the styles being generally light, they are placed side by side on the bench, with their inner edges upwards, and are held by the holdfast; but if the work be heavy, as in carpentry, it must be laid on the mortising-stool, and the operator sits upon it. If the mortise be unusually wide or deep, the greater portion of the wood may be removed by a gouge-bit or centre-bit, and the mortise is afterwards finished by an ordinary chisel.

The chisel is held in the left, and a mallet of proportionate size in the right hand. The chisel is mostly held with its face towards the workman, and the first incision is made about onesixth from the end of the mortise, care being taken to keep the edge of the tool exactly square, and within the gauge lines. After a few moderate blows of the mallet, the chisel should be shaken backwards and forwards to liberate it, and another cut is then made a little in advance of the first, the chisel being slightly inclined instead of perpendicular. If the inclination be sufficient the second cut will join the first at the bottom, and by thrusting the handle of the chisel from him, the workman is enabled to prise up and remove the small wedge-shaped core, which is the result of the two cuts. The chamfer, or bevil of the chisel, is used as the fulcrum, and it acts against the solid wood behind it. When cutting the ends of the mortise, the chisel must be held perpendicularly, and the handle is moved towards the centre of the mortise, to displace the chips, the edge of the tool being the fulcrum in this case. When prising up the chips the chisel must never be allowed to press against the angles or edges of the mortise, or they will thereby be bruised and disfigured.

Having cut the mortise about half-way through, the style must be turned over and finished from the opposite side. Provided the chisel is kept parallel to the sides of the work and strictly within the gauge lines, no great difficulty will be experienced in cutting the mortise true. If the excavations do not exactly meet, in consequence of the chisel going astray, the irregularities must be cut away by a firmer-chisel. A good workman will "drive" a mortise so accurately as to render any subsequent correction unnecessary.

The ends of the mortise are bevilled from the outer edge to the centre, to make room for the wedges by which the tenon will be fixed in the mortise.

Having driven all the mortises, the tenons must be marked from them and cut out. If proper care has been bestowed in cutting the mortises, the gauge lines will be still visible, and it would be only necessary to cut the tenons to the lines which have already been gauged on the rails, to ensure a good fit. As a precautionary measure, however, and one which the amateur ought never to neglect, the styles and rails should be allowed to lie on the bench, their "face" sides upwards, and the ends of the rails must be placed in contact with the inner edges of the styles, and the tenons marked from their corresponding mortises. The pieces should be numbered in the order in which they are marked, to avoid misplacement when fitting the frame together. If the original gauge lines on the rails be found to tally with the mortises, the work is accurate, and we may proceed to cut the tenons; but if there be any discrepancy, new lines must be gauged, and distinguished by short pencil-marks, as the false lines might lead us astray. The lines which were marked on the rails to indicate the internal width of the frame are also correct for the shoulders of the tenons.

One of the rails must now be fixed perpendicularly in the screw-chops, the shoulders of the intended tenon being just above the surface of the bench. Either the tenon or the sash-saw may be used to cut down the sides of the tenon, and the greatest care must be taken to keep the instrument accurately to the gauge lines, which must not be obliterated, but should be visible to the last. Having cut down both sides of the tenon, the rail must be removed from the chops and laid on the bench, and the transverses, or shoulder-cuts, must be made by either the dovetail or the carcass saw. It is immaterial whether the sides or shoulders be first wrought, but the saw must never be permitted to penetrate beyond the lines, or the strength of the tenon will be much impaired.

If the tenon has been properly cut by the saw, it will require no further finish, and the chisel should be used only to clean out the angles between the shoulders and the sides, and perhaps to reduce the thickness and width of the extremity of the tenon, to enable it to enter the mortise. If, however, a few light blows of the mallet fail to send the tenon home, it must be withdrawn, and those parts which show signs of having bound, must be pared down by an ordinary chisel, the flat side of which is applied to the work. Very little should be removed at a time, and only in exceedingly thin shavings. The parts must be again put together, and if still too tight, again separated and "eased." The grooves for the panel must be ploughed in the inner edges of the styles and rails, after the mortises and tenons are finished.