(Photo by Dave Kotinsky/Getty Images for McDonald's)

McDonald's French Fry Box Has a Secret Built-In Spot for Ketchup

Someone on Twitter just posted that the cardboard flap on the top of the box has an actual functional purpose.  You're supposed to fold it back . . . and use it as a place to put your ketchup.

Today Years Old on Twitter

Did y'all know the flap on your fries box actually has a purpose?

So is that the ACTUAL secret, built-in purpose for it . . . or is this just someone's hack?  As of now, McDonald's hasn't weighed in, so we don't know . . . but we DO know that the trick really does work.