Gravity is the driving force behind drainage.
flashing detail penetration Standard wall
With lapped drainage planes such as building paper, the drainage plane material is place beneath the flanged cover, then the subsequent sheet is lapped over the flanged cover. Counterflashing 9. Through-wall flashing is used to divert moisture, which has entered the wall, to the outside, before it can cause damage. Eave Snow Flashing 9. The flashing is extended up the sheathing and lapped 4" minimum by the building paper.
The bottom edge is locked into a continuous 20 oz. Through-Wall Flashing Description: The lower edge is hemmed for stiffness. They are typically handled with the use of bituminous paint, zinc chromate or red lead primers on the contact surfaces.