Samsung Galaxy S III User Manual page 315

2. Tap Screen lock.
 The Screen lock settings menu opens.
Use Swipe to Unlock the Screen
When a Swipe screen is set, you swipe your finger across the screen to unlock the device.
This is the default screen lock on your phone, and offers no security, but you can set special lock screen
options.
■ From the Screen lock settings menu, tap Swipe to save the setting.
 The screen lock is set.
Settings 306