A shower stall with a single knob controlling the shower head contains fewer mechanical parts than a typical bathtub with a faucet and diverter that forces water up the pipe to the shower head when the steel rod is pulled up. One disadvantage to this simpler plumbing system is the inability to shut off the shower head easily if the single knob breaks. You can shut off the water with household tools until you can buy a replacement knob from a hardware or plumbing store.
Cut off the water supply at the main valve in the house or apartment until you can get your tools. This may be faster and could waste less water if you cannot immediately locate the tools you need for the job. The main valve is typically located in a basement or ground floor near the hot-water tank. Turn the knob on the valve clockwise until tight.
Remove the screw in the center of the shower handle or knob. If your handle or knob has a smooth surface, pop off the cover plate with the edge of a flat-blade screwdriver to expose the screw underneath.
Pull the handle or knob assembly straight off the valve stem.
Grip the valve stem with pliers and turn counterclockwise until you feel resistance. With the shower shut off, you can now restore the water at the main valve in the house.