You can create opposite-hand versions of selected components by mirroring about a selected plane. Optionally, you can constrain the original and opposite-hand components to remain symmetrical about the plane.
From the Assembly section of the action bar, click Mirror Component .
For Mirror Plane , select a plane or planar face.
For Components to Mirror , select one or more components from the main level of the current assembly.
To keep the components symmetrical to each other about the mirror plane, click Symmetric Constraint . Otherwise, the components can move independent of each other.