Lemons are a good example of something that works poorly for self checkout. They are small and round which is hard to have a barcode label displayed on. They're

Lemons are a good example of something that works poorly for self checkout. They are small and round which is hard to have a barcode label displayed on. They're worried about weight and that you aren't stealing. It's often much easier to scan a barcode when you're holding the scanner and not the object. Though in this case, you could also just say "lemons" and be done with it.