Matt Hoy writes:

They sell rare earth magnets. Incredibly strong and small. I ordered a
bunch of them. These would be useful for creating the “hard drive killer” door frame [Neal] Stephenson mentions in “Cryptonomicon”. They sell one monster with over 350 lbs of force. I’m afraid I had to buy smaller ones, since I don’t like the idea of breaking a finger when I get it caught between the magnet and a piece of steel.

—Neodymium Super Magnets (gaussboys.com)

Mmmm…. magnets!