OK thanks all. I have a valve that came with a kind of extra lockring thing with a notch in it that might actually be for this. Only just figured it out. Also got one of those things ^^ but it's made of plastic and worked only once before rounding.
s made of plastic and worked only once before rounding.
They are the size and strength they are to stop you over-gronking on installation. That inevitably means they're too weak to get a valve out once it has sat being simultaneously corroded and glued by sealant for a few weeks.
OK thanks all. I have a valve that came with a kind of extra lockring thing with a notch in it that might actually be for this. Only just figured it out. Also got one of those things ^^ but it's made of plastic and worked only once before rounding.