To operate the push-pull mechanism of the rods, you need to loosen the inner nut of the lower rod:
Then tighten the outer nut. That will pull the neck backward to lower the action.
Obviously, you can work the nuts in the opposite manner to raise the action by pushing it with the lower rod.
The upper rod is a different matter. It can only push, because it has no outer nut. Tighten the inner nut to push the upper rod and lower the action.
The upper rod serves to hold the diameter of the head against the pulling action of the lower rod, and is very powerful in its ability to push the neck to lower the action.
That's about it. All you have to do is push and pull with the rods to make action adjustments. Well, there is more.
Some banjos have only one coordinating rod:
These instruments have a more limited range of adjustment because they count on the shell's natural rigidity to take the place of the upper rod.
Many inexpensive banjos have a coordinating rod that looks more like a turnbuckle:
The sad reality is that these rods are extremely limited. In fact, most of them simply don't work. They do serve to maintain the neck angle, but they can't really control it well enough to make a real action change. Pull hard with this rod, and you compress the entire shell into an oval shape. Push hard, and the rod simply buckles and bends.
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