I work often with my notebook at school or by customers, so I need something to quickly lock my screen for security reasons. There is an easy way to lock the screen of Mac OS X and also save battery life.

First check the checkbox for “Require password after sleep or screen saver begins”

Now I create a new active Screen Corner with “Put Display to Sleep”

No I can just move my cursor in the bottom left corner and my screen gets black. After I move my mouse or press a key I need to login again. But all programs run in the background.