Gender of connectors and fasteners



The assignment is a direct analogy with genitalia and sexual intercourse; the part bearing one or more protrusions or which fits inside the other being designated male, in contrast to the part containing the corresponding indentations, or fitting outside the other, being designated female. Extension of the analogy results in the verb to mate being used to describe the process of connecting two corresponding parts together.
In terms of mathematical graph theory, an electrical power distribution network made up of plugs and sockets is a directed tree, with the directionality arrows corresponding to the female-to-male transfer of electrical power through each mated connection. This is an example where male and female connectors have been deliberately designed and assigned to physically enforce a safe network topology.
Although this aspect is not highlighted in their promotional literature, several common construction toys embody gendered (and in some cases, genderless) mechanical interconnections. This should not be surprising, since these toys feature the nearly infinite flexibility and versatility of shape that a modular interconnect architecture can enable. Mathematicians have begun to classify well-known construction sets using group theory to study the combinatoric possibilities of structures that can be built.
Hermaphroditic connections, which include both male and female elements in a single unit, are used for some specialized tubing fittings, such as Storz fire hose connectors. A picture of such fittings appears in Genderless (hermaphroditic), below.
Sheet metal ductwork for conveying air in HVAC systems typically uses gendered connections. Typically, the airflow through a ductwork connection is from male to female. However, since one-way flow is implemented by forced-air fans or blowers, "backwards" gendered connections can be seen frequently in some systems, since all connections are typically sealed with duct sealing mastic or tape to prevent leakage anyway. The flow convention is usually loosely adhered to for simplicity of design, and to reduce the number of gender changer fittings required, but exceptions are made whenever expedient.
A connector in a fixed location is a jack and a moveable connector is a plug. The distinction is relative, so a portable radio is considered stationary compared to the cable from the headphones; the radio has a jack, and the headphone cable has a plug. Where the relationship is equal, such as when two flexible cables are connected, each is considered a plug. Jacks use the reference designator prefix of J and plugs use the reference designator prefix of P. It is possible in the case of box mounted connectors for the connector to be a receptacle with male pin contacts. In this case the connector is designated a jack (J ref des) regardless of the contact gender because the housing for the contacts is in fact configured as the receptacle even though its mate (the plug) goes around the receptacle. See MIL-STD-38999 and similar cases.
In the case of electrical power connections, designers do not reverse connector gender in such a casual fashion, because exposing live AC line power on male connectors is unsafe and generally illegal. Devices that need to be robust against mechanical damage use a special male IEC 60320 C14 connector (see Gallery above), which is recessed below the surface of a mounting panel, providing the desired physical protection while conforming to safety regulations.