The Pan Window shows a smaller view of the image in the Takeoff Window. The black region represents what is currently displayed-such as a zoomed in view. Click, hold, and drag the black region to pan across the image in the Takeoff Window.
You can undock the Pan Window by clicking on its title bar (highlighted in the image below) and dragging it to another location within the On-Screen Takeoff program window, or even outside of the program, like a 2nd monitor.
To re-dock the Pan Window, drop it onto its original location, above the Conditions Window.