On Thursday, President Donald Trump stressed the importance of a particular feature of his proposed border wall: transparency. His reason? Without it, a 60-pound bag of heroin might fly over, and hit an unassuming passerby on the head, striking them dead.

The vivid image invites flashbacks to Chuck Jones cartoons, and more than a few questions. But to take it on its merits: Yes, drugs do fly over the wall. But … not like that. And it has precious little to do with your border wall’s opacity.

'As Crazy As That Sounds'

First, the full quote from President Trump, to establish some parameters of exactly we’re exploring here.

“As horrible as it sounds, when they throw the large sacks of drugs over, and if you have people on the other side of the wall, you don’t see them–they hit you on the head with 60 pounds of the stuff? It's over,” the President said aboard Air Force One yesterday, according to the official White House transcript. “As crazy as that sounds, you need transparency through that wall.”

OK, there's that.

Now I See You

Let's start with the idea that a wall should be 'transparent.' Which, actually, yes. Homeland Security Secretary has said in multiple interviews that the wall would be “see-through,” in parts, which sounds like science fiction, but in practice likely means a chainlink fence, or offset, corrugated steel.

In fact, that’s exactly what comprises much of the 670 miles of existing fencing along the southern border, says Brandon Behlendorf, homeland security expert at SUNY-Albany. “Within urban areas, and even up to 5-10 miles outside of those areas, most of the fencing is 20-foot tall, single or double layer chainlink fencing,” Behlendorf says.

This helps border patrol agents see what's happening on the other side; in cities, it means people can keep eyes on anyone trying to scale or cut through the fence. The practical benefits are less obvious in rural areas, but there's an argument to be made for a see-through fence there, too. Namely, remote video equipment can see through it to take stock of the other side of the border.

“Border patrol likes to operate an awful lot of long-range and photographic and video equipment. It gives them the ability to look fairly deep into the Mexican side of the border, in case anyone tries to come across illegally,” says Patrick Eddington, a homeland security and civil liberties policy analyst at the Cato Institute.

It’s important to note here that neither Eddington nor Behlendorf thinks building a border wall outside of densely populated urban areas makes much sense on any level.

“Fixed fortifications are monuments to the stupidity of man,” says Eddington, quoting General George S. Patton.

“The moment you build a 30-foot border wall, someone’s going to build a 31-foot ladder,” says Behlendorf.

Still, if one intends to build a wall, there are plenty (or at least a handful) of good reasons to make sections of it you can see through. But Trump did not cite one of those reasons. His primary argument appears to be the ability to dodge flying bags of Mexican horse.

Death From Above

The scenario seems unlikely.

Again, chainlink fences typically already make up parts of the wall centered in more heavily patrolled urban areas—not ideal locales for chucking illicit cargo. And that's before you even get to the daunting physics of the toss.

“Whenever cartels try to move drugs across the border, they’re going to try to do that in as remote an area as they possibly can,” says Eddington.

Would a transparent wall, then, help avoid plummeting heroin bags further afield, should someone be walking the unpopulated stretches of the US-Mexico border?

“When you’re talking about remote locations, cartels utilize other technologies. They utilize drug catapults and trebuchets,” says Behlendorf. (In case you haven't taken French combat history in a while, trebuchets are big swinging "siege engines" that usually lob firearms.) "They’re launching drugs not five feet from the wall, or 10 feet from the wall, where a transparent wall would help. They’re launching it 100 feet over the all, 150 feet over the wall. No amount of transparency is going to help you in that context.”

Trump pledged a border wall throughout his campaign; that he has pursued it aggressively comes as no surprise. One would think, though, that he would at least understand what he considers its marquee features–as crazy as that sounds.