The plug holder is a plug built-in accessory used to connect the power cord. Two-pin plug insert: There are two round pins, which only connect the live wire (L) and the neutral wire (N), and are not grounded. Usually this kind of plug can be inserted into any direction of the socket, so that the plug can change the position of the live wire and the neutral wire at will. General pin sizes are: 4.0mm, 4.8mm, 5.0mm.