One of the broken machine screws that had held the passenger side floor in place.
This one came out fairly easily after a good soak in penetrating oil.
Bolt extractors are not very effective (or strong).
And of course a few of the captured nuts were had broken machine screws still in place and had to be removed.
The new floors did not fit well.
New sheet metal floors from vendor’s website.
I had done a cleaning of the handbrake mechanism a long time ago as it was not working when I got the car. It worked when I started taking the car apart. In the intervening years the grunge had been a bit mischievous and the handbrake was not working aging.