The “ports” are holes in the flanges of a spool, made to reduce weight and to provide ventilation for a wet fly line.
Today I am using my rotary indexer to port a group of 5 spools. I am building them as a batch so I can do a lot of anodizing in one day. In my new bronze frame reel design, the spool and knob hardware are the only aluminum parts.
The front flange requires a little more attention. Several ports are omitted, to serve as a counterweight to the knob. And then there are some tool changes to drill and tap the hole where the knob mounts.