Mopar's he would insert a blank key, twist and shake it about to make slight impressions on it, remove it, file impressions a bit and try again until lock opened.
He called it to impression the key. Always worked, but he preferred locked out GM's.
On a road trip from Detroit to Reno for Hot August Nites in my 69 Bee. We stopped in Iowa for the night. Next morning I'm in the shower, the girl friend thinking she's helping out puts my dirty pants in the dirty laundry bag and puts it in the trunk, which was open, the car doors were locked, closes the trunk. I get out of the shower look for my dirty pants to get the keys and wallet, no pants. I ask her were my pants are, she says in the trunk. Call a local lock smith to come out and open the trunk. He used the impression the key trick. Took him about ten minutes.
