In reply to Fraser:
> This interests me as I was wondering the other day how best to ascend a fixed rope. With the set-up shown, how do you descend? (sorry, newb question, I've never used a jumar before!) Is it just by simply lowering from the Gri-gri?
Yes, after see below...
> Edit: sorry, should have added to that last part: doesn't the jumar prevent this, or do you somehow 'unlock' it and just pull it down as you descend?
Indeed, most modern jumars can be fixed to an unlocked position...