Looks like a handyman special to me… If it is 6-10 years old, and isnt leaking, I would file this one under “irregular instalation” and inform the client that the life expectancy of the roof has been shortened by the lack of willingness to pay a contractor, and advise him not to make the same mistake when he re-shingles it. The rusting nails are not good, and always remove metal before re-sheeting:)