Curtain hanger

Curtain hanger with rollers used in extruded curtain rails.

Print the hooks first, then print the rollers up to 6.6 mm by pausing the print. Put the hooks on the rollers, make sure that none of the hooks are pointing up and above the current layer. Resume the print.
When slicing the rollers, keep in mind that you will need space to place the hooks.
The end of the hook can be pushed into a locked position so it sort-of secures whats in it.

I used PETG, anything that is not too stiff could work.