To Mirror References by Using a Fence

Place a fence around the area containing the references to be mirrored.
In the References dialog's list box , select a reference.
Click the Mirror Reference icon.
In the tool settings window, choose the Method: About Vertical Line or About Horizontal Line.
Turn off Use References Dialog List.
Turn on Use Fence and choose the fence mode.
Enter a data point about which the references are to be mirrored.