For 1990-2009 cars

With the key in the ignition switch, you can turn it to four different positions:

Lock: The only position in which you can remove the key. Removing the key locks your steering wheel, ignition and automatic transaxle shift lever. It is not necessary to turn the steering wheel to lock it.
Accessory: An electrical power on position in which you can operate some of your electrical power accessories. Use this position if your car must be pushed or towed. When leaving your vehicle, turn the ignition key from "ACC" position to the "LOCK" position. Then remove the key. This will help keep the battery from running down.
Run: This position is an electrical power on position to which the switch returns after you start your engine and release the key. The switch stays in the "RUN" position when the engine is running. But even when the engine is not running, you can use "RUN" to operate your electrical accessories, and to display some instrument panel warning lights. Never try to push-start your Saturn.
Start: Starts the engine. When the engine starts, release the key. The ignition switch will return to "RUN" for normal driving. Note that even if the engine is not running, the positions "ACC" (Accessory) and "RUN" are electrical power on positions that allow you to operate your electrical accessories, such as the radio and ventilation fan.
To remove the key: Turn the key to the "LOCK" position.

A warning chime will sound if you open the driver's door when the key has not been removed from the ignition.

Notice: If your key seems stuck in LOCK/OFF and you cannot turn it, be sure you are using the correct key; if so, is it all the way in? If it is, then turn the steering wheel left and right while you turn the key hard. Turn the key only with your hand. Using a tool to force it could break the key or the ignition switch. If none of these work, then your vehicle needs service.