Centre Button
  


The Centre Button is located in the centre of the Background and serves two primary functions. Firstly you can move the dock around your display by clicking-and-holding the left mouse button and then moving your mouse; release the mouse button when the dock is in the desired position. In this respect, the Centre Button acts as though it were a Caption Bar of a normal Window.

Secondly, it notifies you of the level (or logical grouping of Dock Items) you're currently working with. At the primary (or "Top") Level, the Centre Button has the image specified for the Centre Button - this defaults to the Circle Dock logo. At the lower levels, this image will be that for whichever Dock Folder item contains the current set of Dock Items.

The Centre Button behaves differently when at the Top Level to when at a lower Level as this table illustrates:
  
 
Top Level
Lower Level
A Dock Item is dropped onto it
The item is deleted (after confirmation)
The item is promoted one level (ie it is moved to the next level up)
Click left mouse button
The Start Menu is displayed (default) or no action.
The next level up from the current level is displayed.