First time I've ever seen one and first use in New York.
It works on the same principle as an extension ladder.
The base of the crane is joined to the building by a dual rail system. One rail holds the crane, the other is fixed to the building. As the building grows, the crane is jacked up the rails. Gravity then acts to swing out lugs which rest on special mounting plates on the building rail. Gravity then holds it in place.
Once above adjoining buildings, the crane will be able to deliver to two sides of the building.
Not a lot of guys willing to walk under it though...
What building is that affixed to? Also, is this the quadrant you were contemplating with scotch the other day?
Sorry, T-1 is the "fashionable real estate selling" name of the Freedom Tower.
And I worry about all the quadrants, but that crane doesn't help.