"DanG" wrote in message
The wooden "knob" on the end where the nail that has the head was
steamed and soaked and squeezed far enough to allow drilling the
center two and dropping the nail in. Once the wood is released it
will return to its original shape.

That's the exotic way of doing it. Another way is to snap one of two of the
knobs off drill them, insert the nail and glue them back. Done properly, the
glue line is all but invisible.