My toilet seat hinge busted, so I'm replacing the whole thing. It's a Duravit Starck 3 seat. I'm trying to remove the old hinges, which are screwed into plastic things that are a permanent part of the toilet itself (there's no way to get inside/underneath, new ones were not supplied). The problem is, as I turn the screws on the old hinges, the plastic things just rotate in the holes so I can't unscrew them. What should I do?
It looks like there should be a bolt with a hex-head that you unscrew using a spanner (wrench) to replace the hinge mounting (the hinge itself appears to be integral to the seat).
It's a designer toilet, designers tend to prioritise visuals over practicality.
If you put some pulling force under part 4 (e.g. lever with a screwdriver using a small dowel as a fulcrum) it might create enough friction on the (presumed) captive nut or insert to hold it in place while you unscrew the bolt.