On a MacBook Air running OS X Lion, I have a dock bar at the bottom of the built in screen, how can I move this to my external screen? I've already got the menu bar moved, but the screen system preference control does not appear to also control the dock location.
The Dock is on the bottom screen if the arrangement makes them overlap vertically.
Otherwise, it's on the screen with the menu bar, e.g. in the following two arrangements:
AFAICT, the reason is that the Dock requires you to move the pointer to the screen edge if it's hiding, and that only works for the bottom-most screen.
You can move the dock with the menubar from the top of the main monitor, if you don't mind that.
At the Display Panel, you can drag the menubar and drop it onto the secondary monitor, and you can see the dock has also been moved to the same screen.
Just be careful that you click on the menubar not the whole screen!
Similar to this tutorial: http://mcreative.tistory.com/148 (in Korean)