To recap, if is the neck is bowed in the middle, the truss rod will need to be tightened. Keep in mind that a little bow is usually a good thing as long as the banjo isn't hard to play. At the same time having a perfectly flat neck may also work well for you. If the neck has a hump in the middle, the truss rod will need to be loosened. If this is the case you've probably been noticing buzzing or notes that sound a bit fuzzy when playing in G or A. It's pretty hard to hurt anything by loosing the rod. Old style truss rods are just metal rods that are threaded on top. There was no way to force the neck back by loosening it. Newer instruments often use rods that work in both directions. The only problem you can get into with these is trying to loosen it too much and stripping the threads on the nut. With these rods the nut is not meant to come off.

Adjusting the rod by tightening the nut is where the possibility of serious problems can occur. BE WARNED! The worst case scenario here is that you tighten the rod too much and break it. This is a really bad thing. It can probably be fixed, but not easily and will cost big bucks. So, ready to learn how?

A little basic info about the truss rod. It runs the length of the fingerboard inside a channel cut into the neck. There is usually a plate covering the end screwed onto the peg head and resting against the nut. Usually two small screws hold it in place. Here's an example:

To adjust the truss first remove the truss rod cover by taking out the 2 screws holding it on. You should see a nut inside a groove sticking out from under the nut. Here's what mine looks like:

The standard size for these nuts is ¼ inch. I described the tool I use to adjust the rod earlier. This is a ¼ inch nut driver ground down on the outside of the business end so it would fit in the groove. I recently figured out that screwdrivers that have multiple bits are also designed to work as a ¼ inch nut driver and usually won't need to be ground down.

As you have probably figured out, my banjo is a Gibson Earl Scruggs model (though I've customized it quite a bit). It's very typical of most currently available high-end banjos. The truss rod system in it may be different from what's on your banjo. This is especially true for beginner level banjos. Most of these have truss rods, but not all do. You can even find banjos with truss rod covers but no truss rod underneath.

Many entry level instruments use truss rods that require an Allen wrench instead of a nut driver. Usually one of these come with a new banjo, but they frequently get lost or were not with the banjo when it was sold. They're usually metric sizes and I can't tell you the exact size. You may need to hunt around for one that works. Hardware stores usually sell sets of the common sizes very cheaply. I've found that many inexpensive banjos have truss rods than don't really work very well or at all. It's not uncommon to find one that has a good sized bow in the neck and the truss rod is a tight as it can get already. Or the opposite may be true: the neck has a hump but the truss rod is completely loose. The main thing to keep in mind is that you shouldn't use a lot of force on this type of rod. Let's get back to our example!