Self-checkout was supposed to make shopping faster and easier for everyone. But as anyone who has waged a war with the bagging area knows, it has also introduced a whole new frontier of frustration.

“Ugh. Where to begin?” Jodi R.R. Smith, the president of Mannersmith Etiquette Consulting, told HuffPost. “Self-checkout is great for when you pop in somewhere and need to grab a handful of items or a quick bite to eat. However, they are simply not designed well for a big shopping [trip].”

“It is difficult to bag, and if the customer has a full shopping cart, the logistics quickly become problematic,” she elaborated. “And don’t even get me started on the poor soul of an employee who is charged with watching all the customers for shoplifting, while fixing the stations as they perpetually glitch.”

And yet, some people manage to make an already imperfect experience even worse.

“Unfortunately, it looks like these machines are here to stay, which means polite customers need to know how to best navigate them,” Smith said.