Castro Valley has 22,242 households, and most of the garages behind those doors went up around a single build year: 1966. That matters more than the town's size on its own, because a place this size, built in one tight window, means the hardware failing right now is the same hardware across whole blocks at once. A steel roller from a mid-60s door has been riding the same track for close to sixty years, and steel on steel with no sealed bearing wears a groove into the track rail over that much time. Once the groove is there, a new roller dropped into it still binds, because the track is the worn part, not just the roller. This is different from a newer subdivision where doors came in over twenty scattered years and rollers fail one house at a time for no shared reason. Here, the reason is shared: the housing stock itself. We see the same track wear pattern on original steel-roller setups across this part of the service area, which runs from 1938 to 2005 overall but centers hard around the mid-60s in neighborhoods like this one.