The Mirror tool reverses the position of a selected model element, using a line as the mirror axis.
You can pick the mirror axis or draw a temporary axis. Use the Mirror tool to flip a selected element, or to make a copy of an element and reverse its position in one step.
For example, if you mirror a wall across a reference plane, the wall flips opposite the original.
To select the line that represents the mirror axis, select Pick Mirror Axis. Or to sketch a temporary mirror axis line, select Draw Mirror Axis.
You can pick only a line or a reference plane that the cursor can snap to. You cannot mirror an element around empty space.
Revit LT moves or copies the selected element and reverses its position opposite the selected axis.
Selecting the element to mirror (and copy) and the mirror axis
Mirrored (and copied) door