tough thing for sure then... at the very least, the next time someone tried to pick up their car and not pay - - I wouldn't be able to find their keys... for a while, then I would go to lunch or have an "emergency" I had to run off to and deal with.. "oops, sorry, got busy and forgot about you" -- you know, leave them hanging out in the waiting room. Of course they would get the keys back right before closing time - along with a verbal notice that no other work will be performed until the balance of this work is paid in full.