Types of locks
Warded lock (凸塊鎖)
A warded lock provides security through a set of obstructions, or wards, inside the lock and a small key hole. The obstructions and the small keyhole are so designed to prevent incorrect keys from opening the lock and other tools from breaking or loosening the lock. The warded lock is the most ancient type of lock still in use today. As it can be easily made, it is also the least secure among all types of locks. Therefore, it is advised that the warded lock be not used to lock any exterior door of a house. Perhaps, it can be used to lock a storage room, an inner room door, or a drawer.

Lever lock (桿鎖)
A lever lock provides security by the use of tumblers, each of which is engraved with a hole of various height. When opening the lock, a flat key with notches is normally inserted into the key hole and rotated clockwise to lift the tumblers to their correct height to press the spring and open the latch. During the process, the key cannot be withdrawn until it rotates back to its original position, a mechanism to prevent people from leaving unattended the open door and the key. Generally, there are two to fourteen tumblers in this type of lock. A level lock with more than six tumblers is regarded as having a higher security level. A safe must be equipped with at least six tumblers and some may be installed with fourteen tumblers. A lever lock can be used for places requiring low level of security, such as desks, drawers, mailboxes, suitcases or safe deposit boxes.
An ordinary lever lock may appear in one of the following three forms:
1. A monolithic lock shell, which is usually welded or riveted with rivets.
2. Suppression patterns. The back and side case of the lock is monolithic, with the side ear bent and the lock case cover fixed on top.
3. Cover is fixed with screws.

Padlock (掛鎖)
Padlock is fastened by a U-shape shackle and the lock body. There are generally three fastening methods: by springs, hooks or steel balls, with steel balls being the best media. The useful life of a padlock is short, especially when it is exposed outdoors. The warded lock is a common design of padlocks, which can be unlocked by rotating the key to open the spring rod to let go the shackle from the lock body. Although padlocks provide low level of security, they are applied in many occasions, such as bicycles, warehouses, basements, toolboxes, cabinets, drawers, and so on. When selecting a padlock, you should consider such factors as the size of lock body, the shackle clearance, the diameter, the material, and so on. A good padlock should have a steel-reinforced shackle, a larger lock body with plating, and a shackle with high tensile and resistance.

Disc tumbler lock (盤簧鎖)
The cylinder of a disc tumbler lock consists of a number of discs, whose outer edges are of the same shape and size but whose rectangular holes are of various length. When a correct key is inserted and turned, all the discs will rotate such that notches in the perimeters line up. This allows a sidebar to drop from the cylinder into the groove made by the lined-up notches in the disks, so that it does not obstruct the cylinder, allowing the cylinder to rotate and open the lock. In general, the number of discs is less than five. A disc tumbler lock provides about the same security level as a lever lock, better security than a warded lock, but lower security than a pin tumbler lock. The disc tumbler lock can be used in automobiles, motorcycles, desks, drawers, bins or coin machines.

Pin tumbler lock (銷簧鎖)
Almost all good locks adopt the pin tumbler lock cylinder. When the correct key is inserted into the lock cylinder, the lower pin tumbler in each chamber falls on the tumbler key tooth. As each tooth is different in height, the lower pin tumbler rises at different height. When an upper tumbler is raised by a lower tumbler but pressed down by the spring from the top, the upper and lower tumblers maintain a certain position, allowing the plug to rotate in the lock cylinder. When the key is pulled out, the lock will be locked because the spring presses each upper tumbler into the plug.

Combination lock (號碼鎖)
A type of lock without a key, the combination lock can be opened by correctly putting in the numbers, turning the dial, or pressing the button on the lock surface. Most commonly used on a safe, this type of lock has a series of tumblers, whose notches can be aligned by turning a correct combination of numbers to let the bar on the lock bolt fall into the gap, thus unlocking the lock.

Type of keys
There are four main types of keys, including Cylinder Key, Flat Key, Bit Key and Tubular Key. Cylinder keys are mostly applied on door locks and padlocks. Flat keys are mostly used on cabinet locks or drawer locks. Bit keys are often used on the door locks. With a hollow cylindrical shaft and a small tab in front, the tubular key is used on suitcases, luggage, drawers, and so on. Types of locks have been increasing. For example, there are magnetic keys for magnetic locks, semicircle lever key for vehicles, the double-sided key with concave on both sides, the pressure key with key teeth placed on the top of the key, and so on.