The invention relates to a covering for roof windows, doors, and the like and to coverings for roofs and facade linings or auxiliary materials for roofs and walls. 
It is known to use a lead apron to achieve water-tight transitions between the covering frame of a roof window and the roof.  In practice the lead apron is adapted to the shape of roof tiles by unrolling the material making up the apron from larger rolls onto the frame downwards and then stretching it to the shape of the roof tiles.  The material is pressed into a depression of the tiles, which causes a crease in the material.  This frequently results in the creation of cracks in the lead apron, through which water can penetrate.  The lead apron is then left directly exposed to the weather, which causes the lead in the lead apron to weather over time.  As a consequence, the thickness of the lead apron is selected to be greater than is actually necessary.  Moreover, a weathered lead apron looks ugly and is perceived as a foreign body on the roof.