GrooveTech Tools TRC-2 Cheater Trussrod Driver

It's more or less an expensive screwdriver at first glance. You can also look at things from a different perspective, as I'm assuming the reason you're even considering getting this tool is because you have a £1000+ guitar/bass in your possession at the moment.

Now, with most of the above type instruments, you can constantly have to separate the neck from the body everytime you need to make adjustments to the truss rod. You will know by now that's a pretty risky activity for such a small task. A more precarious alternative is getting any wide flat-head driver and attempt at turning that old, rusty, truss rod nut while the said driver sits at an angle. The last activity basically will render the nut useless in one careless swoop.

The Cheater rod means you don't have to take that chance. It's exactly machined so it sits exactly in the middle of that cross. Suddenly, spending £10 isn't that extravagant anymore.