There are two methods to adjust gravity hinges on bathroom stall doors. You can either adjust how the door sits in the frame, or you can adjust how quickly and forcefully the door closes itself. In either case, a poorly adjusted door can make using the bathroom less comfortable by compromising privacy or making unnecessary noise as the door slams shut. Neither fix should take more than an hour, but both require some investigation and trial-and-error.
Adjusting the Hang
Inspect each hinge where it screws into the door and frame to check for loose screws. Tighten down all screws. Note that many stall doors come with specialized screw heads, such as hex heads or star-shaped heads, to reduce vandalism.
Swing the door open and shut. If the door is uneven at the top, you need to loosen the bottom hinge. If it's uneven at the bottom, you must loosen the top.
Unscrew the hinge you need to loosen about 1/4-inch at a time. Test the door with each new adjustment until the door hangs evenly. Always do this with the blade of the hinge that attaches to the frame.
Insert enough shims in between the back of the hinge and the door frame to stabilize it into position then tighten down the screws to secure it there.
Adjusting the Tension
Close the door. Locate the tension lever hole in the side or top of the hinge.
Insert the tension lever into the hole. If you can't find the lever that came with the hinges, you can use an unbent paperclip or finishing nail.
Turn the tension lever to the tightest position available for the hinge. Test the door. If it's too fast, turn the tension lever to a slightly looser setting.
Continue to test and set the tension until the door swings at the speed you want it.