@TimWardCam @CiaraNi I now have a cellar full of surplus curtain rail fittings which I am hanging onto as "they might be useful one day". No doubt I will get rid of them in a decluttering purge only to need them the week after.

@CiaraNi And Big Curtain Rail. You move into a house which already has curtain rails, but no sliders/hooks to go with them. You go to buy new sliders, but can't find anyone selling the right fitting. So you end up buying new curtain rails. (This is a UK story. From visits to other European countries I suspect they may use more standard fittings?).