To mirror objects across the working plane:
Select the object(s) to mirror.
Hybrid objects such as walls or columns must remain perpendicular to the active layer plane. If you are mirroring a hybrid object, set the working plane so that it intersects the active layer plane at 90 degrees.
Click the Mirror tool from the Basic palette.
To change the selected objects, press and hold the Alt key (Windows) or Cmd key (Mac) while you Shift-click or click-drag to select the objects. The Selection tool is activated in boomerang mode while the Alt or Cmd key is pressed.
Select Standard or Duplicate from the Tool bar, depending on whether the original object is to remain in place.
Click Mirror Across Working Plane mode.
The object or its duplicate is mirrored to the opposite side of the working plane. There is no need to create an axis line.
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