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) and as a diagnostic aid for bypassing an amp or splitter.
They are VERY useful for bypassing an F connector splitter to check if the loss (on the splitter) is the cause of a poor signal.
Also see CoAx Back to Backs.
Connector shown both ways in the picture, obviously only one (or five) is supplied !