detached garage with a subpanel

2 of them at least 6' apart and #6 copper.

Just drive the 2 rods, run the #6 continuous through the 2 and land them on your ground bar in your panel.

I usually go through the first pulling enough to make it to the 2nd one and the rest back up in the panel.

If your talking about the ground wire between the 2 rods, I just take the claw of my hammer and dig a little trench just to have it underground or secure to the structure.

PS. Drive your rods flush with the ground, be sure to put the clamps on first because the ends flare out and you won't be able to get them on. Also, if it's getting inspected, I'd put some spray paint on the ends so the inspector can find them.

:confused1:Oh, I though your were talking about ground rods for your subpanel..:laughing:

See if this helps
http://www.mrlightning.com/files/diagram-r.jpg

I would say outside.