If you want the whole object to be mirrored over to the other side you have to select the entire object , if you are in component mode just right click on the geometry and slect object mode from the marking menu and select the whole object.
With your pivot point on the center line of the grid duplicate the geometry usind ctrl + D, then in the channel box (top right of the UI ) scale the geometry -1 in the X to mirror it over , then under mesh hit combine and finally select the center vertices and merge them individually.
2 x Modeling Challenge Winner
Last edited by jsprogg; 30-08-2007 at 11:38 PM.