What happens when a driver adjusts the side mirror on a car?
It changes the direction light has to come from to be reflected into the drivers eyes.
The knob that adjusts the driver side mirror also adjusts the passenger side mirror. Simply turn the knob to the right to adjust the passenger side, and turn to the left to adjust the driver side. Leaving the knob in the middle, neutral position will keep the mirrors from changing if the knob is hit.
To replace the driver side mirror on a 2003 Ford Focus you will need a socket and a Philips head screwdriver. Loosen the driver side door panel so that you can reach inside to unplug the wiring harness, and then remove the bolt and screw to remove the mirror. Put the new mirror in place and reattach everything you just removed.