Organising the display with the Layer Tool
    Each graphical view renders a combination of the stored
      images according to the settings of that view's layer tool. You can
      think of the view as being the result of observing a stack of overlaid layers
      with different visibility, transparency, colour, etc., settings.
    The top of the layer list (7) represents the uppermost layer
      of the rendered stack. Rendering is evaluated from the bottom up so
      layers higher up the list obscure those lower down.
    
      
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	    The "Visibilty" checkbox (1) toggles whether or not a given
	      layer is visible. You can also toggle this property by simply
	      double-clicking on the relevant layer in the layer list.Each layer can be locked using the "Lock"
	      checkbox (2). This property determines if a given
	      layer can be edited or not. By default freshly loaded layers
	      are locked, but new layers, those created with the "Create
	      Mask" menu option, are un-locked by default and can be
	      edited immediately.The "Transparency" slider (3)
	      determines how the selected layer blends with the layers
	      below it. A value of 1 makes any voxel
	      above threshold completely
	      obscure the same voxel in the layer below, while a value
	      of 0 means this image makes no contribution to the
	      rendered stack.The "Layer Up" (4), and
	      "Layer Down" (5), buttons move
	      the selected layer up or down the stack. Items lower
	      down are obscured by those higher up the stack.The "Info" button (6) calls
	      up the layer info dialog
	      where you can get a fuller description of an images
	      properties as well as modify some advanced options such
	      as the look up table to be used.The "Layer List" box (7) indicates the order in which
	      the layers will be evaluated along with visual feedback of that
	      layers display settings. |   | 
    
     The layer marked with chevrons (8) to
      the right of it is the "main layer". This layer is the first one
      loaded during any given session and cannot be removed from the
      list as much of the viewer's display capabilities are determined
      from this layer's attributes.