Procession of the Chair Towers

After the convention was over I stayed another day rather than drive home in the dark when I was tired. So I roamed about the deserted hotel looking for things to draw. I found these towers of piled-up chairs in the large auditorium room where our events had been. I sat and drew them, intrigued by their stacked forms, reminding me of a giraffe, or a centipede upright, or a parade of walking skyscrapers. But what I really want to know is, how did the hotel people get these stacked up so high? Did the more nimble workers crawl up the sides to place more chairs at the top? They are too heavy and unbalanced for people to lift to add more chairs from the bottom. So they must have had some sort of machine to do it, like a cherry-picker or something. But I never saw any such contraption. However, there must be a simple answer to this mystery.