Mark installed one of his patented (US7507887B1) double action truss rods into the Honduran Mahogany neck blank today.
https://patents.google.com/patent/US7507887B1/en
Mark’s truss rods are unique in they have two axial threaded sections with differing pitches. When you turn the adjustment nut, it causes the threaded sections to advance at differing rates changing the length of the rod creating a controlled bend. The mechanism provides extremely fine, controlled adjustment. Mark manufactures and sells them to many luthiers. My guitar from Michael Bashkin has one for example.
The truss rod was capped by an Honduran Mahogany insert. He also epoxied in two supportive 3/8” x 1/8” x 18” carbon fiber bars as well.
