Use the COPY_SURFACE_MIRROR operation to copy a surface.

Click on any control point of the surface you want copy.

A new surface is created, with the same control point locations with a 1 metre offset in x, y and z coordinates, followed by x-coordinate signs reversed.

Note that the orientation of the new surface is reversed (so that the normals point in the opposite direction).

Use REVERSE_SURFACE_ROWS to reverse the orientation of the new surface.

Switch between orthogonal projection views and continue mirror copying surfaces.

Click the icon again to disable the COPY_SURFACE_MIRROR mode.

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