Edit: hey, whaddya know, if I hadn't stopped searching at the bottom of page 1, I'd have found the answer, it's on page 2... apologies for the wasted bandwidth.
[quote:zmn06fq0]Hi Vic,
They are a 9/16" ball end driver. We sell them in our web store. You might be able to find one with a screw driver handle locally if you have a well stocked tool store in your area.
The truss rod threads are right handed so clockwise to tighten ccw to loosen.[/quote:zmn06fq0]
So looks like I'll be spending the evening trawling through a drawer full of ikea keys and bike keys and torx keys

/Edit:
Hi,
What is the size of the key for the Combustion truss rod? My luthier [i:zmn06fq0](français)[/i:zmn06fq0] just phoned to tell me he's having trouble finding a key that fits properly.
Is the nut a long way from the opening, so that an extra-long key is required - i.e. do I need to go hunt in my key drawer for the key that came with the Combustion, or will a key from a standard set work?
With thanks and best regards,
- Fletch