The Mirror options allow you to mirror move or copy points using an indicated reference line as the axis of symmetry.
For either option, you will first be asked to indicate the two reference points that make up the mirror line. You will then be asked to indicate the points to be mirrored. Both options obey the current pick mode and so you will be asked to either indicate a point to mirror, sketch a rectangle surrounding those points to be mirrored or confirm that the currently selected points are to be mirrored.
The segment option will mirror the points to a new location on the other side of the segment indicated.
Finally Horizontal and Vertical are mirror lines are indicated by a single point. Once a single point has been indicated a horizontal or Vertical mirror line is created for the points to be mirrored.
Note that these options can only be used if there is no DTM in the current model.