Need help with GH trick and logic

I have sutfaces grouped by two. They come from set of single flat surfaces that were split along centrelines.
I need to group them by LEFT and RIGHT based on a direction of a centre line.

I have tried multiple approaches but none gave me good result.
Any idea?

Assuming the surfaces have uniform normal (if not, join them all and explode).
Pick the mid point P and evaluate the tangent vector T of the curve.
Then with surface/brep closest point find the normal vector N.
Compute the cross product vector V from T and N.
Move P with V (by a small amount is enough).
Surfaces near from resulting point are “right” , surfaces far are “left”.

Writing this was slower than doing directly. For a direct solution, attach your geometries…

I figured it out just the moment you’ve posted. I had to do some bypass

one wrong wiring can mess hugely :slight_smile: It’s late here, bed time, i’m loosing my focus.
Thanks for tip. Much appfreciated.