Flashing are the metal pieces that are formed around joints or the roof, as with a valley between the main house and a garage. These joints divert rainwater down to the gutters for channeling to the ground. In the event this metal corrodes; the joints could become exposed to the elements resulting in interior damage. In the same way that flashing protects low joints, trim protects the seams at the top of the roof, as on the ridge. Keeping the trim intact will protect the interior of your home, as well.
Your intact flashing and trim will help channel rainwater to your gutters and downspouts. During your maintenance inspection, your professional can check these for any signs of leakage. Holes in the gutters and cracked caulking at the seams can result in rainwater running down the sides of you home, resulting in damage to the exterior walls.
Over time, this damage could spread into the interior of your home. Inspecting the downspouts is necessary to check for clogging. Over time clogging by plant material can result in rainwater running over the edge of the gutters rather than running through the downspouts. Checking the outflow of your downspouts to ascertain that the water is running away from your foundation is another task that your professional can perform.