My mom and I had just gotten back from a day of driving around Amish country and we needed to stop at Walmart for a few things. She picked up groceries and was ahead of me in the self-checkout line. There was no visible sign stating that coupons couldn't be used at the self-checkout section, so when she scanned her groceries and then scanned her coupon and it didn't go through, she mentioned this to the attendant.
Mom: The computer's not scanning my coupon. Attendant: Oh, that's because these don't take coupons. Mom: So what am I supposed to do then? Attendant: Take it to one of the checkout lines. Mom: When I've already scanned everything here?
The girl rolled her eyes, took the coupon, scanned it in her computer, and then my mother was able to continue her transaction.
How hard would it be to produce a sign on a computer, print it, and hang it up?