Highlight running applications
To indicate which applications are running in other docks as well as the Process Dock, check this box.
Highlight Classic applications
To indicate any Classic-only applications in your docks, check this box.
This is useful for quickly seeing how many applications you are using which are not yet native for Mac OS X, and to avoiding starting up Classic accidentally by opening one of them.
Highlight mounted disks
To indicate which disks in your docks are currently mounted, check this box.
Mounted disk can also be shown in a single dock, the Disk Dock.
Hide docks when you click the close button
To temporarily hide a dock when you click the close button, rather than trying to delete it, check this box.
You can show a hidden dock by selecting it from the Window menu.
Unselect dock items in background
To unselect any selected dock items as DragThing is put into the background, check this box.
This means that if you open a dock item by clicking on it, it will be unselected automatically.
Click empty spaces in docks to add items
To be able to click an empty space in a dock to add an item to it, check this box.
When you click, an open file dialog will appear which allows you to select the item you wish to add.