Newbie: How to open Sorrow's Furnace gates?

I feel really stupid asking this but this is the first time I've bothered to do the Sorrow's Furnace quests ("To Sorrow's Furnace, Fire in the Hole" for example). I'm sitting here with my henchies, the gates are closed and I'm supposed to scout around, but I can't figure out how to open the stupid gates. I know there's supposed to be a gear wrench or what not, but can't find it.

Sigh.

Any help would be appreciated.

Okay, I feel even dumber. Walk up to any active gearbox (not the one on the gate to be opened) and click the gears (highlighted) and you are now carrying a master gear. Carry that to the gearbox for the gate and click the gearbox and the gate opens.

Moderator gods, close this one if you wish.

Had the same problem a few days ago, until I clicked on one of the gearboxes by mistake (I was aiming for an ore box) ^_^

Chris