Monroville said:
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Of course, you'd have to wonder who made the poor design of putting an antenna for things to get caught on right below a disposal hatch... You would think that when Luke falls onto the antenna, there would already be some clothes and junk hanging off that thing from previous door openings...
It's an exhaust vent, not a garbage disposal hatch. It wouldn't be designed for bits to fall out, so the placement of the vane isn't a big deal.
And I think we are missing the point on the falling chunk of the vane. The reason they put it in there is to emphasize the danger of Luke falling to his death. It's a long way down and that thing falling shows it. It really doesn't matter what it is, just what it does for the movie.