The bank heist sequence was done entirely in one take, with no one other than the principal actors and people inside the bank aware that a movie was being filmed. When John Dall as Bart Tare says, "I hope we find a parking space," he really meant it, as there was no guarantee that there would be one. In addition, at the end of the sequence someone in the background screams that there's been a bank robbery - this was a bystander who saw the filming and assumed the worst.
John Dall and Peggy Cummins did all their own driving in the film, and according to Joseph H. Lewis, only one process shot (i.e., rear projection behind the actors pretending to drive) was used in the entire film.
The 17-page bank robbery sequence was scheduled for a three- to five-day shoot with numerous camera set-ups, but director Joseph H. Lewis decided he didn't want to do it the conventional way. He told the producers he could pull it off in a single day with one shot that never entered the bank. Since that would cut down on production time and eliminate the need for a bank set, the idea appealed to their budget consciousness, but he still had to prove to them it was possible. So he did a test run with extras using his own 16mm camera.
Al J. Jennings, a real-life bank robber from the days of the "Old West", served as technical adviser. He was 85 years old at the time.
In a 1981 interview with author Danny Peary, director Joseph H. Lewis described how he instructed lead actors John Dall and Peggy Cummins: "I told John, 'Your cock's never been so hard,' and I told Peggy, 'You're a female dog in heat, and you want him. But don't let him have it in a hurry. Keep him waiting.' That's exactly how I talked to them and I turned them loose. I didn't have to give them more directions."