A global grid is a 2D object which exists automatically in each 2D
environment (although it is hidden by default). The grid can help the
user to orientate himself better in the 2D working window. It can also help / force
the user to snap the key points of the currently created or modified object
to the grid crossings.
Display (shown / hidden) and behavior (snap on / off) of the global grid depend on the selected drawing option.
Note:
Global grids cannot be added or removed. They
can be selected in the navigation panel only and are available in the Environment
node 
.
Properties
Global grids can be edited in the properties panel. The properties common to all 2D objects are described in the 2D Properties Panel section of this help file.
Editing the object properties of global grids allows changing their distance. You can set the grid lines distance separately in the X and Y axis direction.