My neighbour has a leaking rad with a pinhole along the bottom of it. He used to have a Danfoss TRV fitted on it, which played up, so he removed the main TRV part - so it now just shows the pin - he needs to shut the leaking rad off, with a view to replacing it, but doesn't know whether the TRV end is open or closed - i.e. should the pin be in or out to prevent water flowing...?