What screws do I use with this kobalt k rail

I mounted mine onto a 2 X 6, in my trailer. I used 1 1/4" sheetrock screws, every 6 inches, along the screw seam. I did that because, I change the location and hangers depending on what I'm using my trailer for.

I used the recommended ones (Item #103681, 32 pack black screws). I drilled them into the struts and they hold quite a bit of weight too. You should be able to locate the screws right where you purchased the rail system :)