F connector “Back to Backs” (female to female, also known as couplers or barrel connectors) are used to convert a male plug to a female. They can also be used to join two leads together, see cable joining kit.
These rae supplied without nuts and washers, if the latter is required see F coupler with nut and washer.
F conn BtoBs are VERY useful for easily bypassing an F connector splitter or amp to check if the loss on the splitter (or excessive signal from the amp) is the cause of a signal problems.
Also see CoAx Back to Backs.
Connector shown both ways in the picture, obviously only one (or five) is supplied !