@Sammy93 I'm an upholsterer/seamtress and had to go install some curtains at a rental, which also involved hanging new curtain rods my welder had made. No guests were in residence at the time. So the welder, his helper and I had gone to the property, only to find the door code had been changed, and the property manager, even though I had told him when we were arriving, had neglected to let me know the new door code. So the three of us sat around for about 45 minutes, while I tried to reach the manager, who wasn't answering his phone.
Finally the welder said, "What was the door code before? Maybe they just reversed the numbers."
Sure enough, that worked. I turned to him and said, "You, Sir, have the mind of a thief." We had a laugh about that, but really, that was apparently not a smart door code change- although it would not have occurred to me to reverse the numbers, it obviously would to some.