is that 10mm bolt under the cutout on top of the rail? just one?
I believe there are four per side. One under each cover, and one under each end cap. The end caps just pop off (snaps off) by hand. Takes a bit of side to side and muscle. I did the first one gently with a wrench or a flathead (don't remember) so I could figure it out how it works. Just snaps into place.
Roof trim also just snaps into place - which is why it was easy for some scalawag to steal one off of my car. No tools needed.
2018 Kia LX HEV Metal Stream with Advanced Tech