I am an advocate of tenkara - a form of traditional Japanese fly fishing. Modern Tenkara rods telescope and the line is a fixed length, usually around 12'. Between fishing, the line needs to be stored. This line holder does just that and then slips over the cork grip on the rod. It is similar to commercial Japanese versions but mine is smaller and wider and made of biodegradable PLA!
UPDATE: I realized that this thing did not need to be so wide, so I've created a narrower version that is 5mm between the spool flanges. The original is 10mm between flanges. I like this narrower version much better.
Print in your favorite material - PLA is renewable and biodegradable. Both parts are printed together for convenience. Once printed, I like to sand the edges slightly and the insides of the 8 slots to make sure they do not snag the line. Glue it together with super glue or epoxy.
I am working on a snap together version.
Print them in different colors so you can tell your different lines apart.