Look for short grain and especially any unusual or sudden change in grain direction around the tenon area.

Inside the mortise, after you’ve chopped out the main mortise, pare down the end walls at an angle to gradually widen to the bottom of the mortise, giving room for the wedges to spread into the vacant space and so give it the dovetailed effect that the joint depends on. The distance from the edge of the tenon will mostly depend on the bendability of the wood and how you decide how far from the edge will be no more than a good guesstimate.

In the old days a young guy starting of in the building trade, very soon came across the use of wedges.

If you look carefully, you’ll see some tool manufacturers take this approach on squares and the like. This is the foxed (fox wedged) mortise and tenon `I made a short but informative video for on YouTube and posted a few days ago. Another common use for steel wedges is to raise and position steel columns, a wedge will lift it as required and also hold it in position whilst fixing down and packing. Bear in mind that the maximum cutting capacity of the Rage 2 is 6mm and that the forks are about three inches by 1.

George, my then mentoring craftsman in my apprenticing days, cut the two saw kerfs and said, “ Watch this! It’s good to see additional areas like the ends of the wedges indenting into the bottom of the mortise and the retention properties afforded adjacent to the extended area on either side of the mortise opening. For us novices, drilling the end hole before cutting the slot may also help prevent cutting past the intended depth. You must look at your wood and make the decision for the best position to make your saw kerf, but, that said, I would say that almost any position will do except going too close to the edge. The wedges then serve to fill the gaps causing the play, giving a mechanical boost to the strength of the joint and allowing glue to work properly.