I am tinkering with the idea of using a truss rod in the future but am not sure of the indications when to use one. Based on the research I have done, it looks to be when using 4-6+ strings and no thru n thru neck.
Hi Lonman, in 6 stringers I place them anyway; in 4 stringers depending on my mood and the scale length. To insert a normal threaded rod of 4mm Islot the back of the neck over the whole length. The truss rod is then covered by a wooden strip as cover, while nuts on the ends pretension the rod. In most cases the head stock is not inclined which saves a lot of work.