Using dry ice to freeze the water inside of a pipe at work in order to cut into the pipe to make a solder joint without interupting service to the entire building.
There is a buckle that is attached over the pipe containing water. Liquid Co2 is pumped under pressure to the buckle and expands creating a ring of very compressed dry ice. The dry ice then freezes the water inside of the pipe to create a plug of ice. Once frozen the plug can hold back any buildings water pressure.
So ya.. that's me basicly talking to myself.