A roadblock is set in place when a "friend" goes down a hallway with only one exit. You stand in the hallway upon their return and rip a stanky gas bomb. Blocking their escape and Leaving them stuck in the hallway until the air cleara or having to walk through the funky fart cloud you have created.
Bill went into the closet to get a book. I followed him down the hall, and having chili for dinner I farted and left a roadblock for him. He had to read his book in the closet.