Used with malicious intent or as a hilarious practical joke, a piss brick is a frozen sheet of urine most often prepared in a shallow pan. The brick is then slid under the door of the victim's residence. In the most glorious of outcomes, the urine is absorbed by carpet and establishes its long-lasting odor.
"Should we call the police on your noisy neighbors?"
"No. We'll deliver a piss brick to send the message."