College girls: If you're in an unsafe situation, hold your finger to the screen. When you're safe, let go and enter the 4-digit code. If you let go but aren't able to enter to code, help will be sent to your location.
These life-changing shortcuts are RIGHT AT YOUR FINGERTIPS. These tips are detailed presentation with pictures so I'm sharing the website reference. that some of these tips and tricks will vary depending on which exact iteration of OS X you have.