A few times a week, I drive past a construction site where there is a type of crane I’ve never seen before. It looks like your typical mobile construction crane–I think it’s mounted on tracks–but at the top of the boom there’s a hinged connection to another, equally long boom, which slants away from the crane back down toward the ground. The far end of this second boom rests on a pair of wheels.
Unfortunately, I can’t find a picture of one by googling. Anyone know what this is and what it’s for?