Quote from Adrian Monk in Mr. Monk and the Captain's Marriage
Adrian Monk: Okay. Okay, here's how you follow someone. Stay at least 40 feet back. But not more than 60. And whenever possible, try to use reflective surfaces. Natalie: Reflective surfaces? Adrian Monk: Yeah, see? [looks at Karen in the reflection of some sunglasses] Very discreet. Reflective surfaces. Wait a minute, I lost her. Where'd she go? Natalie: [holds mirror on top of sunglasses rack] Okay, would this be considered a reflective surfaces? Adrian Monk: Yeah, well, mirrors. Mirrors are good, too.