Things To Avoid In Mortising
: AN ANALYSIS OF TENONING, MORTISING, RABBETING AND BEADING
You must be careful to refrain from undercutting as your chisel goes down at the lines a
, because if you commit this error you will make a bad joint.
As much care should be exercised in producing the tenon, although the most common error is apt to occur in making the shoulder. This should be a trifle undercut.
See the lines (A, Fig. 209), which illustrate this.