You can lock the device to avoid accidental key presses, for example, when the device is in your pocket or bag.
Slide the lock switch.
When the keys and screen are locked, the screen switches off and the keys are inactive.
The keys and screen may be locked automatically after a period of inactivity.
|Change the settings for automatic key and screen locking|
Select Menu > Settings and Phone > Phone mgmt. > Auto. keyguard and the desired option.