Abstract: The kit is made from sheet material for flashing a quadrangular roof-penetrating element, for instance a window (4), in an inclined roof (5) with a substantially plane surface, which material comprises a first element (1) with two through cuts (6) extending convergingly from the ends of a first line segment (L1) to an edge (7) of this element (1), a second element (2a) with two through cuts (11, 12), which cuts extend from each end of a second line segment (L2) obliquely to an edge (13) of the element (2a) under formation of an acute angle (V21) with the line segment (L2) and obliquely or straight to an edge (14) of the element (2a) under formation of an obtuse or straight angle (V22) with the line segment (L2), respectively, an element (2b) mirror-inverted relative to the second element (2a), a third element (3) with two through cuts (19), which elements extends from each end of a third line segment (L3) extends to each their respective edge (20) of the element (3) under formation of an obtuse or straight an