A boom barrier or a boom gate is a pole-like structure that blocks pedestrians or vehicles from crossing the particular area where it has been installed. We all have seen boom barriers in the parking lots of shopping malls where they allow entry only after we pay the required amount. They are also used to block traffic too in some cases. Also, we have seen boom barriers in movies where they have been installed in a highly private area or high-security area. You need some ID to enter that particular area and then the vertical arch-like boom barriers open.