AFTER passing through security at the Minneapolis-St. Paul International Airport recently, Nathan Rau noticed something odd -- stuffed animal puppets, actually -- affixed to two electronic wands used for body scans on passengers chosen for more intensive secondary screening.

''They told me they use the covered wands to screen young children,'' he said. ''They said it makes the child feel a little more relaxed during the process.''

Screeners at Minneapolis are using their heads, Mr. Rau decided.

Mr. Rau, a 31-year-old Minneapolis lawyer, has a fairly straightforward approach to evaluating airport security procedures. ''I'll give praise where it's due, but not where it's not,'' Mr. Rau said.

Praise is due to the screeners in Minnesota, he said. But not for the screeners at Dallas-Fort Worth International Airport, who recently confiscated his car key as a prohibited item.

''I'm leaving Dallas on a Sunday and at security it's the usual stuff -- shoes off, laptop out. My carry-on bag goes through the X-ray machine and I hear the infamous 'bag check!''' Mr. Rau recalled.

Here we go, he thought. ''A screener says, 'Sir, is this your bag?' And I say, 'Yeah, and I need a private room if you're going to go through it,' '' he recalled telling the screener.

Mr. Rau explained: ''As an attorney, I carry documents, and because of the nature of what I do -- I do intellectual property law -- opening them up in a public place could have repercussions for myself or for my clients.''

He was told private rooms were for personal screening, not for screening bags. That was not the case in Minneapolis, on the rare occasions when Mr. Rau said he was randomly selected for a secondary screening. ''In Minneapolis, if you ask, they always give you a private room and they're nice about it,'' he said.

At the Dallas checkpoint, the contents of his bag were dumped on the table. ''They pull out my car key,'' he said.

''What's this?'' an inspector asked.

''My car key,'' Mr. Rau said.

Mr. Rau drives an Audi. Audis now come with stylish ignition keys designed to house the key inside a holder, preventing rips and wear on pocket liners. You push a button on a flat two-inch shaft and the key slides out.

As he demonstrated it, Mr. Rau could see the word forming in the minds of the screeners, now three, on his case: switchblade.

''Now the bells are ringing,'' he said. After running the key through the X-ray machine three times, the security committee reached a conclusion. ''Well, sir, that's a switchblade style, and that's a prohibited item,'' Mr. Rau said he was told. ''We're going to have to confiscate that.''