Check the frame first
Same rule as everywhere: push the fence top before ordering boards. On Mountain View's shared side-fences, also check whose rails the boards hang on — repairs on a shared line go smoother when the neighbor hears about them from you first.
One way boards change the answer
Boards that go back the same height and the same material keep the job permit-free. Boards that come back taller, or that arrive with a lattice topper on the run, are measured to the top of what is now there — and past 6 feet that is a planning permit with the neighbors' written consent, plus a building permit. It is the cheapest surprise on this page to avoid.
Next step
Damaged boards straight-on, one shot down the run — through the form for a count-based range.
Board details: see the service page. City rules: see the Mountain View page.