Creating straight lines from bunch of points

i have created a portal frame parametrically. i now want to create lines for purlins from points on each frame in the Y direction. But unable to do so. i tried grafting, simplifying the point list but no avail. Could somebody please guide me?
Screenshot 2021-01-07 035547|690x331
portal (16.2 KB)

Use Flip Matrix.

portal (17.9 KB)

Worked like a charm!

Thanks HS_Kim