A heavy gauge metal lock used primarily for securing bicycles. The U-lock gets it's name from a 'U' shaped metal rod that has cutouts at each end to fit into a horizontal locking bar. This is considered to be one of the best bicycle locks.
Using a 2-5 pound piece of steel, originally intended to lock a bike, to do cosmetic damage to a 2,000-10,000 pound piece of steel originally intended to transport human beings used to purposefully do physical, possibly lethal damage to a human being on a bicycle.
After being repeatedly honked at and passed very closely at high speeds I enacted U-Lock justice. The driver now might think twice before purposefully endangering the life of another human being.
When pansy bicycle messengers vandalize automobiles with their bicycle lock. Usually because they think they are above the laws of the road yet still want to peddle in it so they sometimes have accidents with automobiles.
ME: "Some sissy on a bicycle just hit my car with a lock"
FRANK: "Why did he do that?"
ME: "Dont know, he was weaving in and out of traffic and I almost hit him."
FRANK:"Ahh, in their little bike world they call that U-Lock Justice."
ME: "Sounds like something a 13 year old made up. LOL"
FRANK: "LOL"