The stock and finished sizes are the same as for the halved cross (Lesson 19 (Halved Cross)).

Fig. 80. Through Mortise and Tenon.

This joint is made in a manner similar to the slip mortise and tenon (Lesson 21 (Slip Mortise And Tenon)). The chief difference is that, as the mortise is enclosed on all four sides, we cannot use a saw in working it. Instead of sawing out the mortise you should bore as many holes as can be made half way through from each side and then smooth the sides and ends with the chisel. (See Figs. 35, 36, 71, 73, 74, 75, and 76). This piece should fit together so exactly that it will not require gluing. You should do no work on either the mortise or tenon after the piece has been cut in two.

Dress the end of the tenon flush with the edge of the cross piece by using a plane, as in Lesson 17 (Finishing The Halved Corner), Fig. 61 If the work is well done the face side of the joint will be exactly even when the pieces are placed together It must be considered a very serious defect if the face surface is not even, and you must try diligently to discover the place that is incorrect It may happen that you have the face-marks turned one each way, or that you were careless in drawing the lines, or that you did not draw the lines for both mortise and tenon at one setting of the gauge. Any of these mistakes must be considered quite serious at this time. You should now be able to draw lines correctly and work to them with considerable accuracy. Perhaps you can find the difficulty and yet make the joint correct After you have done your best, finish the ends by sawing as explained in Lesson 20 (Halved Dovetail). Do not plane the sides or use any sandpaper on this joint.