When the shower and the tub continues to run. How do I stop the faucet from running.

We need more details to make a reply. Name brand. One handle or two knobs? How old? Please rephrase your question. What leaks? The stem when it's closed? The spout? The shower head? Both? When do you see the leak? When you run the valve or does it leak even when it's off. Like I said, we need details. Cheers, tom