Ten metre pipe lengths are stored temporarily in the mouse hole while the kelly bar is swung across to screw into the pipe threads. When not in use, the kelly and swivel are secured in the rat hole. (The Petroleum Institute Training Service)

The kelly has sides so that it can be gripped and turned. Turning the kelly turns all the pipe in the hole and drills the hole. (Foster Learning Inc. )

Drilling fluid, better known as drilling mud, is circulated through the kelly and the drill string by means of pipes and flexible hose connecting the drilling fluid or mud pumps and a swivel device attached to the upper end of the kelly. (Kansas Geological Survey)