risk that someone can steal the bike by quickly riding off on it. An O-lock is lightweight and unobtrusive. It can be locked very quickly and conveniently, such as when parking the bike outside a store while running errands. The O-lock also serves as a deterrent to ownership disputes, as the person who has the O-lock key is proven to be the owner of the bike. More recent O-locks have a slot to attach an armored cable, allowing a cyclist to lock the frame, wheels, and seat. O-locks provide a limited degree of security, like all locks. The greatest security requires using multiple types of locks together. In Copenhagen and Japan, the O-lock is generally used alone; the bikes are insured against theft and the owner must show that they have the key, to demonstrate that the bike was locked. The key can only be removed by locking the lock. In other locations, the O-lock is used along with locking the frame to a secure object, or the O-lock is used alone when the owner is very close by, to prevent ride-off theft. Skirt guard A skirt guard (or coatguard) allows using the bike with normal clothes, for both the main rider and a passenger riding on the back rack. The skirt guard helps enable riding in cold and rain because it allows easy use of a coat, cloak, dress, skirt, scarf, or luggage; winter biking becomes possible in conjunction with wearing more clothing and using a skirtguard and chaincase. It also enables transporting various materials on the rack without getting caught in the spokes. A skirtguard prevents winter or flowing spring clothing from getting caught in the area where many features converge: the back brake, O-lock, and spokes. The skirtguard and O-lock form an integrated system. The O-lock catches clothing, so the skirtguard is needed to compensate. The O-lock passes through a hole in the skirt guard. The traditional, old-fashioned city bike has a solid (opaque) fabric skirt guard, while the contemporary European city bike has a clear plastic guard. Fully enclosed chain guard keeps mud off your clothes and maintenance to a minimum A fully enclosed chain guard keeps mud off your clothes and maintenance to a minimum or chaincase enables using the bike with normal clothes and no preparation activity, such as wearing trouser clips or rolling up a trouser leg. A full guard prevents oil stains