The following evening, the new block was made up, carefully fitted, and installed. I have provided a numbered image, as it's a little confusing to tell what's going on here. (If you click on the image above to open the larger one you can see it well.)

1. I always clamp to a "clamp board", a board that spans the whole surface (or near to it) of the back. Its purpose is to provide an overall flatness reference, to prevent the block from shifting upward or downward, as can happen if it is glued "in mid-air." It is a piece of 3/4" cabinet-type plywood (smooth face, no "footballs", and flatter than construction grade.) It is covered with wax paper so I don't glue the zither to it. As I was gluing only at the tail end, I didn't need a clamp board that fit the zither's outline exactly, and since I'll probably never restore another one of these, I preferred not to make a new one for it if I could help it. The one I used was for a No. 73 autoharp, and it worked fine. I had to situate the zither a couple of inches away from the tail end of the clamp board for it to be wide enough, and the exposed couple of inches of it can be seen in the photo.

2. As mentioned, the entire instrument is clamped to the clamp board, and that's what these two clamps are for.

3. In addition to merely clamping the top and back to the new tail block as the 4 clamps at the tail end in the image are doing, the block must also be clamped inward. For this I use a thing I call a "clamp dog." Its purpose is to provide an edge parallel to the tail end of the zither to clamp against. This prevents the block from shifting left-to-right, i.e., in the direction of the instrument's width, which it will do if clamped against an edge not parallel to it. Clamp dogs are also usually made from 3/4" plywood, though 1/2" will normally do in a pinch.

4. Here the excess wood of the new block itself can be seen protruding from the zither's tail end.