Mirror
Modify > Mirror
 

Description:

      The Mirror (Modify > Mirror) command will mirror an object over a world-coordinates axis. If the object overlaps the axis, the overlapping portion will be deleted and replaced by the mirror. All vertices within the merge tolerance will be merged. The axis and merge tolerance can be set in the Mirror options (Modify > Mirror > ...). If the +X axis is selected, for example, all of the object's geometry on the positive side of the X axis will be kept, and all of the object's geometry on the negative side of the X axis will be replaced by the mirror. The object will be divided by the Y-Z plane. The merge tolerance allows for the object to be reconnected if there are vertices close to the dividing plane.  If a vertex's mirrored counterpart is within the merge tolerance from the original vertex, it will be merged with the original vertex.


Notes:

-The mirror operation requires that only one object be selected.