Some kind of door for in spaceships or something. Rotate the rings to open/close.

Edit: I uploaded some new files that should make it easier to open/close it.

Edit2: There's a new Door_part that should prevent the ringthing from snapping when it's all the way open, (in theory. I haven't tested it (yet)). I let the old one online for people who like it ;)

Print 6 parts and remove supports at the rotating point. Print an outer and inner ring. Assemble. Have fun.