[8] All owner-produced parts must still be considered airworthy, by conforming to the aircraft's type design.
An A&P that agrees the owner-produced part is airworthy and that the installation is a considered a "minor repair" can approve the aircraft for return to service.
Some high value aircraft parts can be repaired using various re-manufacturing processes such as machining, welding, plating, etc.
The techniques described in Advisory Circular 43.13-1B are generally used as guidance for repair processes that are not specifically described by the manufacturer.
This means that such a part may not have an approved design, may be manufactured by an unapproved manufacturer, distributed by an unapproved distributor, possibly even taken from scrap aircraft while bypassing mandatory and costly shop inspection and recertification processes.
Indicators for an unapproved or bogus part may reach from missing, incomplete or counterfeit certification, missing or manipulated identification plates, physical aspects like surface grain structure, shape, colour, or weight deviating from the removal part, to any indicators of poor workmanship as well as a suspiciously low purchase price.