My spouse made some curtains and I used wood dowels (1/2"/13mm or 5/8"/16mm depending on the span) along with these holders. The parametric file from the source object was utilized to generate the end and middle supports; the doubled middle supports were created by just duplicating the single middle supports in 3d builder. I used #6 screws to mount the holders to the walls and #4 hardware to secure the dowels to the holders. No screws needed to hold the rods with the middle support pieces and only 1 screw is really needed for the middle supports.

I initially made these out of PLA. They lasted several years but eventually drooped enough that I decided to replace them. Just swapped them all out with ASA copies.