No one knows better than a TSA officer how not to draw the ire of other TSA officers. That’s what the Transportation Security Administration had in mind when it put together a handy list of TSA officers’ do’s and don’ts for travelers to follow. Most of them are rooted in common sense, which isn’t always so common at the airport — whether due to stress or the prospect of missing a flight, some travelers simply lose their cool when they should be keeping their composure. Here are six things TSA officers say they would never do when they’re flying.

Make Ill-Advised Jokes

We all have intrusive thoughts, but there are few worse times to let them win than while going through security at the airport. On the off chance you may be tempted to make what’s obviously (to you, at least) a joke about having a bomb or any other explosive device on you, TSA officers have a few simple words of advice: Don’t do it. The agency isn’t exactly known for its sense of humor (save for its hilarious Instagram account), and even the most offhanded remark will lead to a not-so-friendly chat with an actual police officer that will most likely cause you to miss your flight.

Misuse the X-Ray Machine

Speaking of bad ideas, the TSA checkpoint’s X-ray machine has a very specific purpose — and it isn’t to scan your pet or child. Though you’d think this would be so obvious as to not warrant a reminder, TSA officers have seen it all. In case it’s not clear, babies and/or small animals in carriers should be removed from said conveyance and walked through the metal detector while their carrier goes through the X-ray.

Carry a Gun Through Security

If your firearm absolutely has to travel with you, there’s a right way and a wrong way to do it. The right way is to unload it, secure it within a hard-sided case, and declare it at the airline counter. The wrong way is to put it in your carry-on as a surprise for whichever TSA officer is manning the X-ray unit that day. The former will ensure your gun arrives with you; the latter will result in a bad time for you and everyone waiting in line behind you.

Use Their Mouths as an Extra Hand

With your phone, ID, and boarding pass, you may have your hands full while making your way through security. But that doesn’t make it a good idea to carry any of those items in your mouth before handing them to a TSA officer for inspection. If you wouldn’t want to handle something after it’d been in a stranger’s mouth, neither would they. Take it straight from them: “Your ID is handled by others and goes into a credential reader along with thousands of other IDs. Then you put it into your mouth while you fidget with your phone? Gross.”

Misuse the X-Ray Machine (Again)

It may seem arbitrary to put every single item in a bin rather than directly on the X-ray belt, but in the case of phones, keys, and other small objects, there’s actually a good reason: They can fall between the security belt’s rollers and disappear. If you’d rather not deal with the bin, keep your items secure by placing them in your carry-on bag — that might be a better idea, anyway.

Bring a Full Water Bottle 

Is it annoying and even wasteful that you can’t bring water with you through security? Yes. Is there anything you can do about it other than begrudgingly go along with it? No. The good news is that there are filtered water fountains in just about every airport these days, so you can fill up your reusable bottle and rehydrate once you’ve made it through security en route to your final destination.

However, if you’ve signed up for TSA PreCheck — one of the top tips TSA officers recommend — there may be good news on the horizon. After two decades of the strict liquid rules travelers are now familiar with, the agency is exploring easing those restrictions for the first time. Though no official announcement has been made, according to reports, the TSA is planning to allow PreCheck members to carry a full bottle of water past the security checkpoint in the near future.

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