A one piece clothes pin that should be fairly easy to print out wall thickness set at 1.2mm. I saw one of these made out of bent steel and thought the design would work well out of PLA, so I modeled up the red one ("one piece clip.stl") I thought it might have some teeth that grip a little better and ended up with the green one"one piece clip2.stl" and finally I thought enlarging the spring circle might help functionality so I came up with the yellow one "one piece clip3" added some thicker versions that are 1.6mm thick walls look for the files with the 1_6 at the end, these have the thicker walls upon further assessment I noticed the original metal clip has a reinforcement channel, I have added this to the design, any file with a "improved structure" in the file name should reflect this. "clothes pin lofted3.stl" - MOST CURRENT the last picture is a little misleading it is really only holding the hat because the loose filament acts like velcro I found that keeping the sides attached produced a stronger spring enjoy