The Layer Selection window controls the display of the Earthwork 4D layers. It is activated by choosing Layer Selection from the View menu or by pressing Alt-B.
Clicking the individual check boxes turns the layers off and on. These layers appear as a background to the currently active surfaces layer and can be used to as a reference or to snap data to. Background layers con not be modified unless they become the currently active surface layer. Grayed layers do not exist in the file and are not available for display.
Also see: Strata Selection