A front-on view of a typical pair of Tyco Solarlok solar panel connectors. Although they appear to be a plug on the right and a socket on the left, the left-hand connector is the male connector - hidden inside the socket-like shell is the male plug, which inserts into the centerpart of the female plug on the right. The blue ring on the female connector indicates that this connector is keyed for negative polarity, it would be red for positive. The "keys" that ensure the negative plug cannot be inserted into a positive socket are the plastic fingers extending from the top and bottom of the female plug.