How to bridge edges without creating a twist? I'm trying to model my first car in blender. I started by creating the front wheel arch and then duplicating it and scaling it to -1 in the Y direction to create the rear wheel arch. I then continued to extrude out the side of the vehicle from there.



Now I want to create a bridge between an edge towards the front of the car and one towards the back so I can model the area above the windows. When I select the edges and create a bridge (W > Bridge Edge Loops) I end up with a twist in the bridge:



I assume the edges have inverted Y axis orientations caused by me when I mirrored the wheel arches by scaling -1. I have tried recalculating all normals and playing with the Twist setting in the Bridge tool but I cant create  bridge without the twist.

How can I fix my model so all faces, edges and vertices have the same Y axis orientation again?
With those faces selected use ctrl-n to activate the Make Normals Consistent operator.  If their orientation afterwards is not to your liking, use the Inside checkbox in the operator options panel to flip them.  If you can't find that checkbox, go ahead and use the Flip Normals operator in the Mesh > Normals menu.

If this does not work, then the face sets probably do not share an edge.  Maybe the Remove Doubles operator will fix that problem.  Or you could just select the normals that are facing the wrong way and use Flip Normals on them alone.