The tailpiece is locked firmly to the pot by the nut (and washer) on the inside. The bolt then continues through into the coordinator rod which holds it in position and prevents string tension from distorting the pot.
P.S.
I've seen suggestions that 'adjusting' a coordinator rod can be use to modify the tone of a banjo. So can mashing it with a baseball bat.
The coordinator rod should be mounted 'cold' with no tension anywhere, providing a rigid support to the more fragile wooden parts when you start winding on the string tension.
I use a bench vice to bend these by hand, The curve of the 'hook' is formed by bending at right angles then peening down with a hammer over a 1/8th steel bar. The resulting hook is then trimmed with a hacksaw and file.
I hook the clips over the bottom of the pot rather than screw on a bracket because I just don't like putting screws into such a thin piece of wood then hauling on it.
If anyone wants precise step-by-step instructions on how I do the bends, drop me a line
To make the corresponding holes I use a taper reamer (1 in 20) that I made myself. I just used my metal lathe to cut a 1.5 degree taper out of stainless steel bar then cut a spiral groove down it with a hacksaw. Mounted in a bench drill it makes taper holes perfectly easily although it does make the wood smoke a bit if I really lean on it.
