This same expression "Mind the Gap" is a good one to remember when flashing dormer areas at a roof. The photo below shows deterioration of the siding. At the top, you can see a piece of metal flashing.
Fact is, there was a metal flashing installed at this dormer -- I think retroactively. It had not been there forever on this older home. However, even when they installed the flashing, they failed to trim the siding to end above the roofing material. As it is, the siding had been absorbing water for years. This photo shows that deterioration and weathering, with some decay.
If you are building or remodeling, take this advice: Install a metal flashing and don't forget to "mind the gap".
Steven L. Smith
Bellingham WA Home Inspections