On your car, pop off the plastic trim piece and remove the one bolt/screw that holds the metal outside trim piece on. Do you have the mirror yet? If it's the usual pre-'86 style with the adjustment handle on the inside, it should include at least the mirror, outside trim piece, inside trim piece, inside handle, and a screw. The screw goes through the handle and trim on the inside and screws into the mirror on the outside, holding it to the door. It's simple to install. Once you get the mirror on and adjusted to where you want it, make the screw really tight because the mirror will move at high speeds because of the wind.
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Volvo 240 Links