I'm imagining something a bit like a paint roller with a bunch of patterns around the rim, or an IBM Selectric ball, where the raw materials keep rolling around on the outside until the finished product hits a special protrusion that causes it to fall away.
That is a fairly accurate concept of how a single PKS "module" works- which extends a growing carbon chain by 2 carbons, plus whatever side groups or modifications it makes to those 2 carbons. Then the entire thing is passed to the next module to repeat, and so on down a long linear "assembly line" that you can think of like the conveyor belt that moves a car down a factory one station at a time.
