Ah, I see it. It was kind of a subtle thing so I guess I missed it. The concept now makes much more sense.

Okay yeah, that part is a little confusing- basically, it's meant to be a sort of pillar that the sliding door halves lock around- when the door opens, the pillar lowers into the floor, allowing passage. The light basically indicates whether the door is open or not- often, it's activated by a terminal.

Also, I think I need to update this with a little phasing- it doesn't really make any sense that the arch braces on the far left and right open while the doors themselves are opening- they should unlock before the doors open.

 Finally, something new from you! This is a really cool piece, I can already see other tiny spaceships flying out of there. The only thing I'm confused about is that the flashing red and green thing stays there.