Security has always been a concern for all of us, specially when we are in our office. For which it is necessary that we lock our machine whenever we leave our workstation. Were you been on a PC, you would have tried Ctrl+Alt+Del and clicked on Lock Computer or Windows+L can do the job. Being on Mac very few of us actually know how to lock the machine using shortcut. Let’s learn it here Open up the System Preferences and open the Security section. Now make sure that you have set you computer to require a password once the screen saver begins or once the computer has woken up from sleep as below. Now when you hold down the keys Control+Shift+Eject your screen will go black and after 5 seconds your computer will then require a password to log back in.