You Shall Not Pass
I showed this comic to my wife and she just sneered and said, “that wouldn’t stop most women; they’d just march right in. It’s boys that have the problem going into washrooms.”
Oh well. I still think it’s funny and possibly the one way you could prevent adventurers from just immediately blundering into a chamber. You can lock the door and that’s just a speedbump. You can disguise the door as a wall. You can ward the door with magic or build-in a horrible deathtrap. None of that will stop adventurers from trying to get through that door and into the adjacent room. But put a gendered sign on the door…
A clever solution to stop inventive players!
I remember instead the infamous cerebral parasite, or “ear tick” in 1st edition, put there for the cautious adventurers who used to press their ears to every door and stand listening for a while, trying to guess what they would find in the next room… At that time seemed to me a cheap way to try fixing the “problem” caused by clever players and encourage head-on dungeon crawling, something you can enjoy when you’re in the range 10-14, but then you start to use your brain and discover the limits behind the D&D system.