Extrude only?

I created complex profile with over 70 quads to be extruded to form an object. It is one half of the form so that it can be mirrored. But, when extruding faces, Blender will create new face at the starting surface to close up the object and create a volume. I don’t need these faces at the mirror line. How do you stop this “closing” function?

That’s normal. You’re extruding faces, it creates faces.
Just extrude the edges or vertices that form the face you want to extrude instead.
Or extrude faces and delete the extra face (x > Only Faces).

Ok, so Blender doesn’t have the option not to create faces. With C4D there is an option not to create it. I thought of erasing the faces but then I needed to select over 70 polygons you know. And they are all bunched up together; extruded and nonextruded faces that is. But than after a while I realized I could select them all at once form edge on view with the box selection.

if you select a face and extrude, you’ll get a face. if you select an edge and extrude, it will fill in appropriate faces. It’s assumed, usually, that extruding means create more visible geometry. If you want to duplicate your faces/edges, whatever, use “d” and move/scale.
help me understand why you want to extrude without faces. could you post a screenie of what’s happening to your model? it generally won’t close in a volume if it isn’t already.

I made this mesh layout using Retopo tool of a Dodo bird. First thing I did was to extrude the whole thing to add some depth at the central portion of the bird. But Blender creates faces on the mid plane where mirror modifier need to located. The image next to my mesh layout shows Mirror Modifier and vertices pulled out to give volume.


So where is it you want to extrude.

Try duplicating the faces using Shift+D immediately followed by zero (0) so that the duplicated faces don’t move. Then use Alt+S (Shrink/Fatten), this will move the duplicated faces away from the original mesh the same as an extrude would but without the joining faces.