Slates span from front to back. They are designed to take the hammering, not your cargo or the painted parts of the roof rack. Standard slates are black Polyethylene plastic strips. They are maintenance free and very tough.
For more character and a natural look, wooden slates can be ordered for the Little Swift™. They are lighter (1 kg) but will need some maintenance in the long term.
Due to the closely spaced load bars, the Black Swift™ can be ordered without the front to rear polyethylene slates.