Seat belt mounting

[Geoff Butcher]

While I was installing my new seat I noticed that the bolt holding the seat belt to the sill is rather rusty. I wondered what exactly it's attached to as there doesn't seem any way of getting at it. I didn't dare trying to undo it in case something horrible happened...

[manifold]

Hi Geoff, Its a square plate with a captive nut...which may or may not be riveted in (I assume before the sill was laminated in).