Definition: Urinal Cakes

From Wikipedia:

Urinal deodorizer blocks, also often called Urinal cakes, are the small disinfectant blocks found in urinals.

The purpose of these blocks is to disinfect and deodorize washroom urinals. Placed above the urinal drain, they are air-activated and slowly evaporate when in contact with the air. Since they do not dissolve in water, they do not deodorize the flushing water and urine.

*My only experience with urinal cakes, before now, was when I took summer chemistry at the men's high school next door.