I have an office chair where the locking mechanism needs tightening. I think the right way to do it is turning this nut, but the problem is that the space is so tight that if I get an adjustable or open-end wrench in I can't turn it. Is there some kind of specialist tool for this kind of job? I think some kind of very thin open-end wrench with a ratchet on the open end could be what I need, but they seem expensive and hard to find.
EDIT: As you can see in the image, it is a very tight fit with an open-ended wrench and there are some metal rods the wrench hits that limits the range of motion even more.