I once tried to walk into a federal courthouse with a knife in my bag. In my defense, I’d forgotten it was there, so when the officer monitoring the X-ray machine asked, “Is there a knife in your bag?” I said no.

When he opened the bag and held up the knife, I said, “Oh, yeah, there is a knife in my bag.”

Why was there a knife in my bag? I’ll get to that at the end of this column. First, I want to revisit my Monday column about the poor guy who was manhandled onto the tarmac at LaGuardia Airport when someone confused his vintage camera for a bomb.

The passenger who freaked out over the camera — apparently not recognizing what it was — overreacted. Presumably, the man’s carry-on luggage had been screened and okayed by TSA before he boarded the flight.

We like to criticize TSA agents, but that can’t be an easy job. Nobody wants to be the person who let something dangerous through. And every year, people try to board with guns, knives, throwing stars, fireworks, sword-canes, hand grenades and smoke bombs. That doesn’t even count the half-filled water bottles that passengers have to either dispose of or chug.

But I’m more interested in benign items that are confused with dangerous ones. For example, before the coronavirus pandemic, Steve Schattman and his wife used to travel to Paris regularly, often stopping at an outlet mall outside the city that included a Bodum store. That’s a company that makes those French coffee presses.

“This particular day they were having a sale on the small personal press. It was ridiculously cheap, slightly over the equivalent of $10, so I bought one,” wrote Steve, who lives in Chevy Chase, Md.

A week later they were at the airport for a flight to London. Steve had the glass coffee press in his carry-on, since he didn’t want it bounced around and broken inside his checked luggage.

“As my carry-on is going through the X-ray machine, the operator stops it and calls over the supervisor,” Steve wrote. “The supervisor looks at the screen and calls security. They take me behind the machine, show me the screen and say ‘What’s that?,’ pointing to the coffee press.”

Steve’s bag was pulled from the belt and he was asked to open it.

“As I’m doing this, I notice everyone is backing up,” Steve wrote. “I get the press out and they see exactly what it is and everyone starts laughing almost hysterically. They slap me on the back and tell me to have a nice flight.

“When we left London to fly home, I had the good sense to take it out of the bag when we went through security so there wouldn’t be a repeat performance.”

I’m surprised the French didn’t recognize the distinctive shape of their national coffee maker. Do Italian airport guards have trouble with those decahedral moka coffee pots?

About 10 years ago, Malcolm Keen was going through security at Heathrow when the chiming mantel clock inside his shoulder bag started to ring.

“A visual inspection of the timepiece brought on fears that it might be a time bomb,” wrote Malcolm, who lives in Fairfax Station, Va. “Why a terrorist would go to that level of complication when a simple push of a button would do the job as well, I have never fathomed. An inspection of the inner works of the clock through its rear door was, in this case, sufficient to soothe the troubled breast of officialdom.”

I wonder if they were worried Malcolm was trying to smuggle Big Ben out of the country. (And, yes, I know: Big Ben is the name of the bell, not the clock, that is in the Palace of Westminster. I don’t want to get into a Frankenstein/Frankenstein’s monster debate.)

What about you? Have you ever been pulled from a security line because of something in your bag or on your person that didn’t look quite right? Send the details — with “Magnetometer moments” in the subject line — to me at john.kelly@washpost.com.

Now, about that knife. This happened back in 2003, when the country was especially antsy over anthrax, nerve gas and other evil pathogens. I wrote a consumers’ guide to gas masks. To test one, I brought an onion, a cutting board and a knife to a personal safety company in Germantown.

I donned one of their gas masks and diced some onions. It worked. I smelled nothing.

Weeks later, that knife was still in my bag when I went to the courthouse to cover a trial. Fortunately, that encounter didn’t end in tears. The guard simply locked up the knife until my visit was over.

Twitter: @johnkelly

For previous columns, visit washingtonpost.com/john-kelly.