On page 16 in the manual you're told to install the rail stoppers, but there's no mention of nuts being shown before page 18. Makes more sense to mention it the first place you use them. Props to setyte#5616 @ discord
I also encountered this issue. A first timer may assume that they need to be screwed directly to the extrusion, which wouldn't be possible. Moving the note from page 18 to page 16 would easily fix the issue
On page 16 in the manual you're told to install the rail stoppers, but there's no mention of nuts being shown before page 18. Makes more sense to mention it the first place you use them. Props to setyte#5616 @ discord