Automobiles have had side-view mirrors since the early 20th century, but the mirrors did not become standard equipment until the 1950s and '60s. The side-view mirror allows you to see what's going on in the lane next to your car so that you can make safe lane changes without having to turn your head. The side-view mirrors are usually mounted near the front of the driver's and passenger's doors and stick out several inches, making them susceptible to damage from hitting objects close to the edge of the roadway. If the mirror head is not damaged, you can save money by replacing only the mirror glass.
Wear gloves to avoid getting cut by broken glass. Use a scraper and finish removing any broken pieces of glass or residue from your mirror head. Use a hair dryer to heat up any glue residue to make it more pliable and more easily removed. Be careful not to mar or scratch the mirror head.
Clean the replacement mirror glass with warm water and a soft cloth. Do not use chemical cleaners, which would will leave a residue on the glass and make the adhesive not stick as well. Let the glass air dry thoroughly.
Cut off the end of a tube of silicone adhesive 3/8 inches from the end with a utility knife. Apply silicone to the mirror frame in several 3/8-inch dabs--but not too close to the edges, so that excess silicone does not squeeze out from the edges of the mirror.
Press the replacement mirror glass into the mirror frame. Move the glass as needed to get it into the correct position before the silicone sets up. Hold the mirror into place with masking tape until the silicone is dry. Check the directions on the label for curing times, which may be five to 24 hours, depending on the outside temperature.
Remove the masking tape after the silicone has fully cured.
To fix your mirror glass quickly and cheaply, buy a universal mirror glass replacement kit. The kit includes a flexible sheet that you can cut any shape mirror from using tin snips. The material is self-sticking once you peel off the paper backing. This is a good temporary solution until you can obtain a glass replacement.