This hanger slides into a common curtain rail slot system. It accommodates a little hook used for hanging curtains.
Print in PLA or ABS.
I printed it on its side with supports.
35% infill is recommended.
It works well this this curtain hook designed by upjohns:
https://www.tinkercad.com/things/eNQE8O2iOMj-curtain-hook
The author marked this model as their own original creation.