United States Postal Service is violating Natural Security Administration guidelines about dealing with terrorists, but it seems to be working.
Terrorists based in a miserable central Californian town regularly mails letter bombs to their perceived enemies. They're largely unskilled in the art and science of bomb making; more than one device has prematurely exploded in the hands of the mail delivery driver.
To protect themselves, the postal workers have begun dumping liters of Safety-Gel in the letter boxes. Safety-Gel deactivates the bomb, but it also ruins most of the mail. Ironically, another terrorist group based in the same town has threatened the post office people with physical violence if they ruin another letter.
Why can't people just get along?
The terrorists and the postal workers finally arrived at a working relationship. The postal workers have designated one mail box that won't get the Safety-Gel treatment; its contents will instead be x-rayed. In exchange, the terrorists have agreed not to put any bombs in the x-ray only box. It's an uncomfortable relationship, but life can be that way.