Ah like this one from "Journey to Babel
" where the ladder goes further down into the deck. It looks like it has a panel covering the opening in this scene though. Also note that the hallway next to it is *narrow* just like the one from "Charlie X"! Looks like the narrow hallway isn't a one-off
This ladder is different from the ladder seen in "Mudd's Women" where the ladder goes up and it stops about midway to the floor. It has no side grating as well. It looks like the same ladder seen in "Mirror, Mirror" that is used to climb up to the EMM. You can get a clear view of it in the scene later in the episode where one of the women is walking back to Mudd's cabin.