Which type of adaptor is utilized to connect two female couplings?

The correct choice is the double female adaptor, which is specifically designed to connect two female couplings. This type of adaptor features female threads on both ends, allowing it to link two hoses or pipes that have male ends.

Understanding the context of couplings and adaptors is key here. In firefighting and other plumbing applications, the ability to connect different sections of hose or pipe is crucial for effective water flow and supply. Using a double female adaptor ensures that both ends are compatible with male couplings from separate hoses or equipment, facilitating a seamless connection without leaks.

The other options do not fit this function. A double male adaptor, for example, has male threads on both ends and would be unsuitable for connecting two female couplings. An adapter coupling generally encompasses various types of fittings and does not specifically indicate the connection between female couplings. Lastly, a wye is a fitting that branches off a single line into two directions and also would not connect two female fittings directly.