Neck ReinforcementThe neck needs reinforcement to counteract string tension. In the center is a two-way truss rod. By turning a screw (accessed through the soundhole), you can bend the neck forward or backward.
I also put 1/4" x 3/8" carbon fiber rods on either side. Carbon fiber is extremely stiff, making the neck much stronger without adding weight. I use Moses Graphite rods; theirs isn't as stiff as some, but that lets the truss rod do its job better.
The rods are put in long before the neck gets to this stage, but I forgot to take a picture at that point.