When people talk about a door lock, they often refer to the lock cylinder, but in reality, the lock itself is a separate element of the door's mechanical system. This article will explain the structure of a conventional door lock. ![Locksmith California](https://hackmd.io/_uploads/H1hnN3IQyl.jpg) image source: https://locksmithcal.com/locksmith-in-victorville-ca/ # Understanding the Door Mechanism A door lock is more than just the small slot where you insert your key. The security of a door relies on a combination of elements: the lock, cylinder, protective fittings, and strike plate. Together, these components form the door mechanism, which consists of several parts. The key components include: * Mortise Lock * Lock Cylinder * Bolt * Latch * Door Handle At its core, most door mechanisms work in the same way. When you press down the door handle, the bolt retracts, allowing the door to open. The bolt and the latch hold the door securely in place when it is closed. Typically, the latch is beveled, allowing you to simply push the door shut without using the handle. To lock the door, you need both the key and a lock cylinder. The key turns the cylinder, which then moves the bolt into the opening in the door frame. In professional-grade cylinders, there are spring-loaded pins inside the core. When you insert the key into the cylinder, it pushes the pins down, allowing the lock to turn. At the same time, the locking cam rotates, lifting a lever that engages with the lock's mechanism. This causes the latch and bolt to retract. The type of lock determines how the lock mechanism is structured. **Types of Locks and Their Mechanisms** The simplest lock is the flat [key lock](https://hackmd.io/@locksmithca/locksmith-california), commonly used in interior doors. There are about 100 different key profiles for this type. Since these locks can be easily opened with a wire, they are not suitable for exterior doors. In contrast, the profile cylinder lock is typically used for exterior or office doors. This is a security-grade lock and offers a large variety of key profiles. Additionally, profile cylinder locks often feature an emergency or safety function. This function comes in handy if you accidentally leave the key inside the lock, as you can still unlock the door from the other side. This type of cylinder is known as a double profile cylinder. The WC lock, as the name implies, is used for bathroom or toilet doors. Turning a knob locks the door, and a red indicator appears on the other side to show that the bathroom is occupied. In an emergency, the door can be opened from the outside with a coin. **How Important is the Key Card?** The key card is a crucial safeguard against unauthorized key duplication. If the key and cylinder are protected with a key card, the key can only be copied when the key card is presented. This is particularly important if the key is lost or found by someone else, as the key card ensures that it cannot be duplicated. For landlords, this feature offers a significant advantage. After a tenant moves out, there's no need to immediately replace the entire lock. The protection provided by the key card ensures that the key has not been copied. **How Important is Burglary Protection?** Drill protection is a critical feature to prevent the core from being drilled out. Burglars use various techniques to break into locks. Typically, the pins inside a cylinder are made from brass, which is easily drilled. However, locks with drill protection feature pins made from hardened steel, making it much harder to drill through them. This makes it much more difficult for burglars to break into the lock, offering increased security. **The Rise of Standardized Mortise Locks** A few years ago, box locks were the standard, but now mortise locks have largely replaced them. One key advantage of the mortise lock is its standardization. Essentially, a mortise lock is a cassette that contains the mechanism for locking and unlocking the door. If any parts of the lock break, it is often more cost-effective to replace the entire mortise lock rather than just the individual parts. At the top of the mortise lock, there is a square opening, known as the square nut, into which the door handle is inserted. The handle can be either a knob on both sides or a handle on one side and a knob on the other. The square nut also operates the latch when the door is locked, allowing the door to be opened.