I work with a guy who used to be an aircraft heavy maintenance tech. We were discussing formal tool and component accountability procedures for a high quality line we are working and I asked how rivets and other fasteners in aircraft are accounted for as they are not serialized.
Tech: "They're not"
Tech: "You sweep and vacuum out the rivets and fasteners from wing tanks and whatever the best you can. That's why the fuel system has strainers and filters."
Tech: "Well, yeah, they have their limits. Thats why on your Airbus or Boeing the fuel intakes are not in the lowest part of the tank. Sometimes if the wing is gutted we will pull all the crap out of the sumps. Usually they're there forever"
Tech: "To really eff things up you need a socket head floating around or similar, that's why we have accountability at that mass level. Every part, every shift"