Mirror (edit) (interface)/0.99.5a

Mirror is a retractable set of functions from Model editor's edit menu.

That function applies an axial symmetry along a plan perpendicular to the selected axis: It emulates the reflection of a mirror that copies half of the object into the other half. In both case, the mirrored half is the one closest to the origin of the coordinates.
 * either to the whole model if nothing is selected
 * or to the selected voxels

See also diagonal function.