The piece is two sheets of steel, carefully welded together around the edges, with a pipe going into a small space in between them. It was heated up in a gas forge, and Elizabeth is blowing it up with compressed air--which you can do because hot metal is a lot softer than cold metal.
Ransom Notes is a fun game, and you might want to click on this picture to make it bigger (especially if you are not looking at this on a phone) and read everything in this picture.
The way the game works is that you have a random assortment of words and you have to use them to convey the message that is on the card, which is sitting in the middle of the picture.
I think Schell took this picture.
