This design is not particularly wind proof. For outdoors use, I recommend my newer revision: https://www.printables.com/model/832264-flag-clip-revised
Hybrid clip / carabiner 3D printable model to attach flags to the rope of a flag pole.
The gate of the carabiner does double duty as the lever of the clip.
Spring mechanism inspired by https://www.thingiverse.com/thing:1212828/remixes
2022-07-03 Revision 2.0
The original version offered very weak resistance against wind, and had a fatal tendency to let the flag fly away (I apologize, but I did not have a wind tunnel in my basement, so this defect only became evident in practical use). The newer version is considerably more resistant against wind, even though it still failed in a particularly heavy thunderstorm. It also tries to accommodate a variety of rope diameters — just slip the clip until it reaches a hole small enough to hold on to the rope.
The author marked this model as their own original creation.