Assign Your Droid Bionic a Password
Perhaps the most secure way to lock the Droid Bionic screen is to apply a full-on password. Unlike a PIN (a code between 4 and 16 numbers long. It contains only numbers, 0 through 9), a password contains a combination of numbers, symbols, and uppercase and lowercase letters.
Set the password by choosing Password from the Choose Screen Lock screen; here's how to get to that screen:
At the Home screen, press the Menu soft button.
Choose Location & Security.
If no additional lock is set, choose Set Up Screen Lock; otherwise, choose Change Screen Lock.
If the screen lock is already set, you have to work the lock to proceed: Trace the pattern or type the PIN or password to continue. You then get access to the Choose Screen Lock screen, which contains four items: None, Pattern, PIN, and Password.
The password you create must be at least four characters long. Longer passwords are more secure but easier to mistype.
You type the password twice to set things up, which confirms to the Droid Bionic that you do know the password and will, hopefully, remember it in the future.
The phone prompts you to type the password whenever you unlock the screen. You also type the password whenever you change or remove the screen lock.