This rod holder purchased from Amazon Atwood 12708-2 PVC rod holder has an open end and a slot for the a reel to stop the downward travel. I wanted to use with a Tenkara type rod for an antenna mast. I drew this cap to keep the rod mast from sliding through. When used as an antenna mast for and end fed, most of tension will be sideways and not straight down.  I glued the cap on mine to secure it, but am not expecting to apply much force against the cap - more just keep the rod from sliding through and passed the rod holder when in use. I used PETG for my print.