A physical barrier object class now exists in the game. From this object, several different objects will come into existance for the sole purpose of getting in your way.
The basic notion is that these things is that they are too heavy to pick up or move from the room they are in. They can be moved into position in front of an exit in the room and will block people from using the exit from -either side-. It's easily possible to remove the barrier blocking an exit from the blocking side, but from the other side, its a pain in the ass.
The command to get through one of these blocked exits it 'charge <exit>'. If you have an appropriate tool for the task (IC Information), you'll get appropriate messages. Stats/skills and monkies are all involved in determining how fast you'll get through the barrier.
Several such barrier objects are now in the game, and more will come as appropriate.