In the transcript of the Apollo 11 EVA on the Moon, Buzz Aldrin mentions closing the LM's hatch and being careful not to lock the two astronauts out.
109:41:28 Aldrin: Okay. Now I want to back up and partially close the hatch. (Long Pause) Making sure not to lock it on my way out.
Why bother closing it at all, why not just leave it open?
Bonus question: Could they have actually locked themselves out?