Sleep second display I have an iMac with a Thunderbolt display attached.

I know I can force both displays to sleep by pressing ctrl-shift-eject.

How can I force only one display, the Thunderbolt one, to sleep?

I do not use both displays all the time and sometimes I just don't want to waste the electricity.
There is no direct control of this for an individual screen in Mac OS as you also can't go the other way round and turn off the laptop-display to only use the external one without closing the lid and keeping it closed.

I guess you have to not plug in your external monitor if you don't want to use it.