Anywhere 3 or more sides of a roof drain into a common area or anywhere standard flashing does not pertain to roof projectiles, like in back of chimneys, are places where pans are needed.

Often owners are unaware that these areas exist on thier roof. If they were fabricated from tin, they need to be painted regularly.

If they are fabricated from copper, they are also prone to the same wear holes as valleys. (notice the roof cement patches on the pan)

Many times these critical areas are more prone to poor workmanship because most workmanship is not visible in these areas, however, they do act as a collection point and are more critical than valleys.

A copper pan that was installed behind a steeple on a church in Harrisburg, PA.