FYI, BVR, the wooden plank underneath the real car is there because of rules stating that F1 cars have a minimum ride height of 50mm, with up to about 3mm leeway for manufacturing faults. The plank is placed underneath the car to tell the ride height during the race and it is allowed to wear away slightly during a race or qualifying session but if the erosion exceeds 3mm by the time that the race has finished, the driver and the team may be excluded from the final standings of the race.
The wooden plank was most notoriously known for an incident back in 1994 when Michael Schumacher won the Belgian GP but was later disqualified (and given a 2-race ban, I think) because the wooden plank beneath his Benetton had eroded too much due to his car having too low a ride height.