Double female connectors are used to attach which type of coupling to another?

Double female connectors are specifically designed to connect two female couplings together. This means that when you have two hoses or pieces of equipment that each have a female coupling, the double female connector serves as the intermediary to join them. This setup is commonly used in firefighting and industrial applications where the transfer of water from one hose to another is necessary, and both ends need to accommodate female couplings.

The correct option emphasizes this purpose, as only a double female connector can facilitate this type of connection without any mismatch in coupling types. Male connectors, by contrast, would require male couplings to engage with them, thus making the other options inappropriate choices for the function of a double female connector. Understanding this functional distinction is crucial for proper equipment handling and ensuring effective connections in various operational scenarios.