Now you're going to measure the amount of relief in the neck. That's the amount of bow that's in it. Now on a guitar you want it to be as straight as possible, usually. On a bass, there are a few basses out there that can be dead straight, but generally they play a little better with a little bit of a bow, or relief, in them. What I like to do is take a straight edge and put it on the neck itself. You want to look at the gap between the straight edge and the bass neck or the frets. This neck has a little more relief in it than you want, so what you're going to want to do is tighten the truss rod. If there was not enough relief in it and it was too straight you would loosen the truss rod.
In order to do that you have to loosen the strings. Some, even Fender basses, more modern ones, have truss rod access at the top of the neck. This one has it at the bottom, which means you have to take the neck off in order to do this. You want to take your driver, throw it in reverse. I like to not take the screws all the way out. They need to be all the way out of the neck itself, but you can leave them in the guitar. It's a little bit easier to put it back on. I'm going to lay it down, pop the neck out. Take a nice flat-head screwdriver, a big one, and tighten it up a little bit. You want to go, unless it's really loose, a quarter turn. Then tighten it back up.
You can only tell what the neck relief is when it's tuned at the pitch, so every time you make an adjustment, you're more likely going to have the guitar need tuning, so you'll need to tune it back up to see what you did. Some guys like it to be really straight. If you have a really straight neck you're going to need higher action for it to play right. I'll tune it up now. G. You want to take your straight edge, put it down the middle of the neck, look at it, and it's still got a little bit of bow but not too much and that's really what you want. This is really a matter of personal preference. Some guys like a lot of relief in the neck. I find that they play a little better when there is just the perfect amount.