A car sun visor that moves unexpectedly while you are driving could cause an accident. An older visor can sag or sway, either blocking your vision or falling out of the way of the blinding sun. Tightening the sun visors in your car can be done with tools you may already have.
Put on the safety goggles to prevent being hit in the eye with falling screws.
Align the sun visor into its proper position, both with the mounting bracket in each corner and with any clipping mechanism the visor may clip into.
Remove the screws from the mounting bracket with the Phillips-head screwdriver. If the sun visor was hanging, sagging or swaying for a long time, the screws may be at an improper angle or damaged. Removing them will correct this.
Move the sun visor so the holes in the mounting bracket and the holes in the car's headliner line up. Screw in each screw by hand at a straight angle until you can't turn it in any further.
Move the sun visor up, down and to the sides to test its snugness.
Don't over-tighten the screws, which could strip the screw holes. If the sun visor still hangs or sags, try using slightly longer screws.
If your car is under warranty, check with the dealership before trying even simple repairs. Doing the work yourself may void the warranty.