From the Assembly section of the action bar, click
Mirror Component
.
Selections
Mirror Plane. Specifies the
plane to mirror about. Select a plane or planar face.
Components to Mirror.
Specifies the components to mirror. Select one or more
components. Selections can be parts or subassemblies, and must be from the main level of the current assembly.
Options
Symmetric Constraint.
Preserves the symmetrical position about the mirror plane between
each mirror component and its seed component.