Method for joining a vehicle body component and vehicle body component

The process involves pressure setting of an air-tight unit (2, 6) against a support (3) of body part (1), and fixing a dressing unit (4) on the support such that the unit (2, 6) ensures air-tightness between the unit (4) and support. The pressure setting involves the use of a spacer forming unit (5) placed between the unit (4) and support (3). The unit (5) allows to exercise pressure on a part of the unit (2, 6).