‘Disappearing’ skid blocks a part of F1’s flexi floor tricks:
https://www.motorsport.com/f1/news/disappearing-skid-blocks-flexi-floor-tricks/10335974/
"... It is suspected that some teams have cleverly split up the skid blocks, which protect the holes where the FIA plank thickness measurements are taken, in to separate sections.
There is a main skid block that runs around the majority of the hole, but then a more rearward section that moves up and down independently within the plank to become fully enclosed and protected if the car hits the ground.
By disappearing up inside the plank, this section does not get worn down as the rest of the floor hits the track – so remains at its original thickness throughout to be fully compliant with the previous 9mm depth checks that are conducted by the FIA after races.
Up until now, teams only needed to ensure enough thickness at one area of the hole to comply with the rules – so the moveable part of the skid would have no problem passing this.
From the Belgian Grand Prix, when the new floor stipulations will come in to force, the FIA’s checks on the thickness are being changed.
In the draft TD sent to teams ahead of the British Grand Prix it noted: “we wish to confirm that compliance with this Article will be required around at least 75% of each periphery.”
This means that teams will no longer be able to use small areas of moveable skid block material to help comply with the rules in a single area. ..."