Sometime you may have large compilation (kernel?) / download, yea and you are bored to do anything else on your laptop, if so you may have puzzled about how to manually switchoff the laptop screen. heh, if you haven't i have ;-).
We make use of 'xset' and 'dpms' to handle this, i have assigned a keyboard shortcut for my KDE.I have also anticipated about the security so i use 'xlock' too.
xlock & xset dpms 1200 1800 2100 ; sleep 2 ; xset dpms force off;
Assign the above command sequence to a keyboard short cut, your DE will have such a feature, KDE and xfce do.