20-ton slabs of concrete... with a 2 dollars padlock.
I worked for a nuclear power plant, and one access to the reactor building was through a 20-ton slab of concrete on the yard outside. It had the tiniest padlock, the kind I wouldn't even use on my bicycle, securing it on the ground.
I laughed, but then I got the explanation: that was a SEAL, to show signs of TAMPERING, or signs that something inside the building had gone possibly VERY wrong. Like, "steam blast pushing 20 tons slabs out of place" wrong.
If you get past security with a 20-ton hydraulic arm truck and manage to lift that slab without proper authorization there would be some chewing around... and in an emergency, security can authorize the slab to be raised like the padlock wasn't even there.
I spent 4 years getting by that padlock snickering and thinking how clever it was afterwards...
While outside the plant, in the nearest neighborhood, distribution had a problem in their hands: the switchgear cabinets kept having their padlocks broken, but no gear or copper stolen from them... those were old-school brass padlocks, most valuable to junkyards. Once replaced with steel ones, nobody stole them anymore.
Not IT related, but I found parallel to these padlocks in computers, like those darned hardlocks used for CAD sofware...