The plank on an F1 car is a mandatory attachment to the underside of the car that is designed to impose a minimum ground clearance and to limit the use of ground effects to enhance handling. It is a flat rectangle, usually made of a wood composite, that is fitted beneath the central plane of the car. The plank is used as a gauge to restrict the minimum ride height attainable by the car. The closer the car is to the ground, the more efficient the front wing and rear diffuser. However, cornering loads can push the car down much lower to the road, which can be dangerous. The plank was introduced to counteract this and to ensure that teams are running the correct ride height and to prevent teams from running ground effect aerodynamics. The plank is typically made of a homogeneous material and must extend longitudinally from a point lying 330mm behind the front wheel center line to the center line of the rear wheels. It must have a width of 300mm with a tolerance of +/- 2mm and a thickness of 10mm with a tolerance of +/- 1mm. The thickness of the plank is one of the parc ferme tests, and if it is found to be worn beyond the allowed limit, the car is disqualified. The plank does not in itself restrict airflow under the car, and it is not designed to create sparks. However, titanium skid blocks are embedded within the plank to prevent it from getting damaged, and they protrude out from the plank itself by no more than 3mm. When the car bottoms out, the skid blocks hit the ground first, creating a shower of sparks behind the car in the process.