^those are the rollback fins that pop up after the train launches (hydraulicly). They are just an extra/really needed safety thing. Look at ttd, which rolls back daily, along with that green thing. (yes, I do know it's name...) If you look at the peice, the cable/catch car go in the middle little trough, and they are connected to a big room of hydraulic thingys! (I'm so good at describing things!)