From the TV series The Universe:
The speed of light is the ultimate velocity in the universe. lt's Einstein's cop on the block. The speed of light is so fast that you could go around the Earth seven times in just one second. For you to jump to the Moon, at the speed of light you could reach the Moon in about one second.
I'm guessing block means area and the speed of light is similar to a policeman in that both don't allow law to be broken: Light doesn't allow anything to travel faster, and a policeman doesn't allow anyone to break the law.