Did you know a trapdoor entrance can be a one way door, trapping someone inside with the new 1.9 changes. In this pic we cannot fit into the entrance as it is. Here the entrance is now accessible, by stepping onto the one trapdoor that is down. Once on the trapdoor we can now open the one above it and walk into the building. However, once inside, we are stuck. Open and close the trapdoors all you want, not getting through... This is a nice troll for your minecraft noob friends. heh.