One of the many procedures slowing things down at TSA security checkpoints in airports is the policy of having travelers remove laptops from their bags. Laptops are typically placed in bins and run along a conveyor belt, then reunited with their owners further down the line—unless, of course, it’s hiding something sinister.

But what’s the point of that? Why can’t imaging machines simply see through a simple laptop bag?

It’s not the bag but the laptop itself. According to Science Alert, the components of a laptop—including its battery—are often too dense for standard airport X-ray machines to visualize. Someone could, in theory, take advantage of that blind spot and attempt to use the laptop to obscure a weapon or other prohibited item stuffed inside the bag. By removing it, screeners can get a clear look at both the laptop and its case.

But do they really find anything? Yes. In November 2022, TSA officials discovered a knife tucked inside the chassis of a traveler’s laptop at Richmond International Airport in Richmond, Virginia. (The man initially denied the knife was his.) A month earlier, a loaded gun was found inside a laptop bag at Bradley International Airport in Connecticut.

Removing your laptop may not be a necessary nuisance for much longer, however. In summer 2022, the TSA began rolling out more sophisticated CT scanners in major airports that allow for more detailed views of luggage and algorithms that can detect prohibited items. Agents typically allow laptops to remain in their bags when these CT units are available. Maybe one day travelers will be able to leave their shoes on, too.

This article was originally published on www.mentalfloss.com as The Real Reason You Need to Take Your Laptop Out at Airport Security.