My friends have a split foyer home with a railing on the main level right next to the door. For whatever reason, I felt like it would make a nice place to hang coats when we visit. The railing is 1" (25.4mm) square, so the internal sides are 26mm. I recommend printing at around 50% infill. They fit quite snug, don't slide around, and hold up my big, double-layer jacket quite well.
Model available at [ thingiverse.com ].