[jonknee]

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.

[mattmanser]

Like a lemon's an idiom, sorry! I just meant that it takes a while to get good at scanning.