What type of flashing prevents water from running down the wall and getting behind the base flashing?

Counter flashing is specifically designed to provide protection against water infiltration in roofing systems, particularly at areas where the roof meets a vertical surface, such as a wall. It is installed on top of the base flashing and is meant to redirect any water that may flow down the wall, ensuring it flows over the base flashing rather than getting behind it. This is crucial for preventing leaks and water damage.

Counter flashing works in conjunction with other types of flashing, but its unique role in addressing the interface between vertical and horizontal surfaces makes it essential in keeping water out of vulnerable areas. Other options like step flashing help direct water down the roof, while kickout flashing is used to direct water away from the wall, and drip edge flashing helps manage water runoff at the eaves but does not fulfill the same protective function against wall infiltration.