On Sun, 18 Mar 2018 12:14:01 GMT
John Waterhouse m
wrote:

I was thinking of having some
large double ended wood screws made from hexagonal bar. One end
would have a standard "clockwise" thread whilst the other would have
an "anticlockwise" thread. ( Like the thread on left hand bicycle
pedals except these will be double pointed wood screws of course).
This way, the screws can be tightened with a spanner on the hexagonal
bar in the middle.

Screws don't hold well in end grain. How would you fill the gap that
would have to be left for the spanner?