Our store-bought towel rack disintegrated, so I figured I'd make my own.
Design
I included a hole that goes all the way to the screw to make mounting easier. No need to muck about with angled hex keys or what not, a regular screwdriver will do.
The part that clamps on to the rod is slotted to allow for a bit more flex.
Hardware
It uses a standard .5" (12.7mm) pipe which is commonly used for small curtains, and I've included some endcaps to make things nice and tidy.
Material choice
I printed mine in PLA, seems to hold up fine in humid conditions. I was worried about mold developing between layer lines, but that hasn't been an issue for the 3 years that I've used this.
Printing
I recommend using 4 walls and 20% infill. No supports needed.
The endcap diameter is 12.65mm to get a good friction fit, you may wish to scale this up slightly.
.STP included for easier derivatives.
The author marked this model as their own original creation.