The present invention provides a swivel sub for connection in a work string between a workstring and a downhole apparatus. The swivel sub includes a first substantially cylindrical body, including a sleeve portion having one or more teeth and a second substantially cylindrical body being partially located within the sleeve portion. The bodies are arranged to rotate relative to each other. The swivel sub also includes a sliding sleeve, having one or more teeth arranged mutually engage with the first teeth is axially moveable between disengaged and engaged positions, in one embodiment by a pressure differential being created in the sub. Further, the present invention provides methods for of running the tool, with particular application to setting and hanging of liners and screens.