Horrible sleeping conditions. Bad food. And boring tasks.

That’s what you can expect if you ever land at job at an iPhone factory, according to an ex-Pegatron employee and NYU grad student who went undercover at one of Apple’s factories in China.

President Donald Trump has called on Apple to bring iPhone manufacturing jobs to the U.S., but if Americans learn what it’s really like inside an iPhone factory, filling those jobs might be impossible.

While Apple has made considerable efforts to improve working conditions at its factories in Asia, former Pegatron employee Dejian Zeng experienced firsthand that there’s still work to be done.

In a wide-ranging interviewing with Business Insider detailing his job, Zeng revealed that he only got two days of training before being sent to work on the iPhone assembly lines. Pegatron gave him the monotonous task of putting in a single screw on the iPhone’s speaker.

He worked at the iPhone plant for six weeks last summer and explained what it was like when the factory transitioned from iPhone 6s production to the iPhone 7. The entire process is obviously very secretive. Security even increases the sensitivity of its metal detectors and adds more checkpoints.

Assembling the iPhone 7

“Here’s how it works. Our factory, when we got to working they are already assembling the infrastructure of the assembly line. They have this curtain circling it so you can’t even see how the infrastructure is, right? We were working at the same workshop. But there are people doing construction there. And then after they’ve finished construction and need to move people in, we were moved out and working in another building of the factories. And then they prepare everything and everybody moved back in. And then, producing iPhone 7 at that point it was a trial production. That kind of experience is totally different from when we produced iPhone 6S. Because that’s a whole day, and I consider it as torture. Because one day for 12 hours you only produce five phones. You sit there and have nothing to do, waiting for two hours. Sometimes they don’t allow you to speak. You just sit there quietly and have nothing to do and wait until the next phone comes in. You’re trying to assemble it, and then you put it back and you wait for another few hours for the next one to come in.”

During the switch to iPhone 7 production, Pegatron turned the assembly room into a clean room to keep all the dust out. Workers had to use lint rollers to clean all the dust off before entering the room.

All that down time can be unbearably annoying for employees who aren’t even allowed to talk to each other, read or sleep while waiting a few hours for the next iPhone to come down the line. Zeng says after being spotted dozing off three times he was forced to stand the rest of the day.

The entire interview is well worth a read if you want a glimpse into the lives of the people that make the technology our digital world runs on.