These are terms that you may often hear when discussing all types of locks. In this article I am going to explain each term and also explain how they relate to the security level of the lock itself. It's important to realize that key-drop a lock a certain way does not change its inherent security level. In other words, key-drop can't change a medium level security lock to a high security lock by keying them all different. You can however, lower the level of a high security lock by master key-drop , this will be explained later.
This is where all of the locks are the same. This means that every lock will use the same key to open them. All will be cut the same.
This is where the locks will only have one key that opens them. For example, key A will only open lock A not lock B and key-drop B will only open lock B. As many keys as needed can be cut for each lock.
This is where all of the locks are key-drop different and one key, the master, will open all of the locks. A "Master System" is usually computer generated to keep track of the number of locks and keys used in this Master System. Master systems can get very complicated and have many different levels. You will find these types of master systems in commercial applications such as schools, hospitals and government buildings, to name a few.
The best keying option to preserve the security level of the lock is keyed different; however, that isn't always the most practical. Keyed alike lowers the security level and master keyed lowers it even more. This occurs by making the lock easier to pick or otherwise compromise. However, starting off with a good quality higher security lock will mitigate the keying option that you choose even master keying.
When choosing a lock, try to plan how it will be used in your keying system. The more complicated the keying system the higher the quality the lock should be. The security usually directly relates to the quality and price of the lock. The higher the security level the better the lock quality and the more it will cost.