In a scene in Avengers: Age of Ultron, many of the other Avengers had attempted to pick up Mjolnir, Thor’s most powerful weapon, but ultimately failed. Thor showed everyone off by picking up the hammer. Tony Stark a.k.a Iron Man, accuses Thor of having a thumbprint scanner.
Inspired by that scene, a tech-genius had created a copy of Mjolnir using electromagnets and a thumbprint scanner. He placed Mjolnir on metal surfaces and challenges the people who walk by and see if they are worthy enough of picking up Mjolnir.
After the inevitable failed attempts, the creator would use his thumbprint to pick up Mjolnir. Some were bright enough to catch on but even when they do, they have to admit it’s a pretty creative trick!