This is a paddle holder for kayak track.
I recommend ABS or PETG. The one pictured is in PETG.
Everything but the molds is pretty self-explanatory. The base rubber is made the same way as the wheels mentioned below.
I designed the molds to be injection molded with oogoo (Silicone 1 caulk, acrylic paint, and a PINCH of baking powder.
This is the wheel mold printed, but not assembled. You'll need a .25" rod to insert in the mold as well.
Mold assembled with the .25" rod in place.
oogoo made with blue acrylic paint.