A bicycle chain lock is a popular security tool used to prevent bike theft. In South Africa, where bike theft can be a concern, these locks offer a reliable method for securing bicycles. The lock consists of a chain made from hardened steel links, often covered with a protective sleeve to prevent damage to the bike frame. The chain is secured with a locking mechanism, typically a key or combination lock. While not as secure as other locking methods, bicycle chain locks provide a balance between portability and security, making them a common choice for everyday cyclists.