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.