This is an outdated model. Use these instead: https://www.printables.com/model/1410891-curtain-hook-v2

A hook to bundle your curtains off to the side of the window. Held on with double-sided tape.

It can be printed with no supports if the hook is laid on its “spine” as it should be by default (see the last picture for how I placed them).

I printed them in PLA with 0.2mm layers, 5% gyroid infill, no supports.