The following windows can be "un-docked" from the main interface and can be moved to other screens or "re-docked" within the main interface in different locations: Document Browser, Document List, Work Product Inspector, Thread Visualizer, Who to Whom, Keyword Analysis, Tabulate, and Date Histogram.
To un-dock a movable window double-clicking the title bar of the window OR click on the title bar and drag it away from the DWR interface (i.e. ripping it off).
To re-dock a movable window, double-click the title bar again and it will re-dock into the DWR interface. Drag a floating window over the DWR interface and a docking guide (pictured in the middle of the screen shown below) will appear to specify where the window to should be positioned inside the DWR interface. Drag the window onto the desired directional indicator and let go and the window will dock in that location.
The directional indicators help you re-dock floating windows