A sliding means with built-in moving-magnet linear is disclosed, which makes it possible to sense accurately a table position with a magnetic sensor element. A spray device applies the liner material to the interior surface of the ducts and the spray device is held in the center of the duct by retractable sets of wheels. The motor vehicle protection system cover sheet has at least one supplementary traction appendage having a first end constrained to the sheet and a second end adapted to be fixed through coupling means on the body so as to put in traction the portion of the sheet intended to cover the roof of the motor vehicle downwards.