Ok be interested Pepe. My sons a ticketed welder and even if I want to change the seat mounts (which I do to put in explorer seats) I need an invoice from an engineering firm to prove they did the work or I can't get certified. No certification = no Warrant of fitness. In NZ you have to get a "warrant" every 6 months displayed on the windscreen. Caught without it, its truck off the road and $300 fine.