I am confused.

If you look at the original Maton brochure for this style of guitar:

http://matonmuseum.com.au/data/pdfs/...rbyrd%2070.pdf

It talks about a "Double Thrust" truss rod (very '60's marketing right there). Does this mean you adjusted it from both ends, and that it was designed to distort (bow) in length?

Also, what is the bit sticking out at the back of the truss rod drawing?