To Mirror an Entity
Using the Mirror command you can create copies of draft entities, unattached symbols, and unattached notes by mirroring them about a draft line straight entity.
1. Click > 
Mirror.
Mirror.2. Select detail items to mirror; then click the middle mouse button. You are prompted to select the line to mirror about. You can select the following entities for mirroring:
◦ Drawn line
◦ Construction line
◦ Draft axes
◦ Draft datum planes
◦ Snap lines
◦ Model datum planes that are perpendicular to the drawing sheet
◦ Model datum axes
◦ Model Edges
When you select the line an entity, the mirror copy is created opposite the original, equidistant from the center line.
 | For mirroring you can select any model edge that appears straight. This includes circular or non-straight edges in a model that have their line of sight perfectly straight in the drawing view. |
The following are not a part of straight entities, and hence are not supported as mirroring planes:
• Straight-line entities within dimensions
• Straight-line entities within symbols
• Leader lines on symbols, dimensions, and notes
• GTOL control frames
• Half view lines from Half Views
• Entities in formats