Mirroring a selection. Usage . To mirror a selection along a particular global axis, press: Ctrl-M, followed by X, Y or Z.The image Mirroring a Selection shows the results of this action after a mesh element has been duplicated.. In mesh mode, you can mirror the selection on the currently selected Transform Orientations by pressing the appropriate axis key a second time. Useful when dealing with meshes which are mostly symmetrical, but have vertices which have been moved enough that Blender does not detect them as mirrored (when X Mirror option is enabled for example). This can be caused by accident when editing without X Mirror enabled. Symmetry And Line Of Symmetry : An Introduction. In geometry, <b>symmetry</b> is defined.