The third layer is the stretcher, which has decorative veneer (Courbaril) on its upper surface. All three layers extend to the front of the assembly, but only one, the shelf, is mortised into the rim on each side. The other layers simply sit on the shelf, and between the sides of the instrument. My miserable description will become more clear when we start to take apart the instrument, as the entire pin-block stretcher assembly will be removed.
I no longer joint sound-board panels with the machine, ultimately the hand plane does a better job. Unlike the hand plane, the machine Jointer produces a series of little scoops, the frequency of which depends on the feed rate of the work. A dull machine also tends to crush the wood cells, rather than cutting through them, which can cause a poor glue joint. At least one manufacturer of pianos is still jointing sound-board panels this way. In the first picture you can see the very simple jig, or shooting board, that I use for jointing thin boards. On some, more traditional shooting boards, there might be a wooden hook at one end to hold the work. My jig uses small C-clamps (see below). With the work clamped in place the board can be planed with the long, 24 inch, jointer plane. This keeps the edge square, and saves the worker the trouble of balancing the plane on the thin edge of the board, were it clamped vertically. How force is applied to the hand plane, determines whet