I spent the evening replacing this leaking control valve for one of our upstairs showers.  In order to gain access, I had to climb a ladder and then down into a small hidden chamber behind the shower wall.  The space was barely shoulder-width wide and my first task was to fashion a set of built-in stair rungs so I could climb in and out.  The project took several hours and I had to battle claustrophobia the entire time. Jeanine was close at hand to lower parts and tools in and out from the top.  Despite the very cramped working conditions, I managed some very nice soldering without starting the house on fire or burning myself.  In addition to replacing the control valve, I added two cut-off valves, a new shower head, and a tub downspout.