when you purchase BNC adapters, you should have an idea on what makes a female slot and what makes a male slot. knowing their differences is important in this case. now, so you would know this, the ends of the bnc connectors are what can tell you whether they are male or female. a connector is female if there is a hole in the end of it. the connector, meanwhile, is male if the pin is at the center of one end of the connector. you can easily distinguish the male from the female connector because it has a locking mechanism that allows it to connect with the female connector.