Using sheet metal materials to create protective barriers and seal in building construction, flashing primarily is to prevent the infiltration of water, air, and other elements at critical junctures and transitions within the building envelope. Flashing plays a crucial role in maintaining the integrity of roofs, chimneys, and windows by directing water away from vulnerable areas and preventing potential damage or deterioration. It is an essential component of weatherproofing and waterproofing strategies in architectural design.