What is the best way to mirror lots of vertices? I got this vertices setup on one side of the blade:


What is the quickest way to duplicate this vertex setup to the other side, without having to manually do all the loop cuts and try to match the original side? I can't do mirror modifier, because the other side is supposed to be flat
Select the whole mesh (A) and unselect the nonmanifold edge loop (Shift+Alt+RMB while hovering the cursor over it). Duplicate the selected vertices (Shift+D) and scale it along the X axis by 0 (S,X,0). Finally remove doubles (W-->Remove Doubles).