Wouldn’t it be nice, especially in an office or educational setting to be able to lock your screen from the Mac OS X menu bar? Here’s how to do it:
1. Launch the “Keychain Access” application located in /Applications/Utilities.
2. Choose “Show Status in Menu Bar” from the View menu.
3. Now you have a lock in the menu bar. Use this menu to:
Lock the screen (activates Screen Effects which requires your password to unlock screen).
Lock or unlock your Keychain.
Launch the Keychain Access application.