Locks and keys

Different locks suit different purposes. Their effectiveness depends on:

• strength
• strength of connections to doors or windows
• complexity

Different types of locks

• Locks fitted to the surface of a door - fine for cupboards holding low-value goods.
• Mortise locks - fixed within the structure of the door and the doorjamb. five-lever locks are the most secure and suit external doors. However, the door and frame must be strong.
• Padlocks - work well when used with strong chains and fixings.
• Combination locks - opened with a unique number. Some need two people to open them, each knowing only one combination.
• Access control systems - release a lock if people give certain information. They might type in a PIN (personal identification number), or swipe a plastic card through a reader.

Key policy

Keys can be easy to copy or lose. Restrict the number of key holders and choose locks with keys that are only available from the manufacturer. The lock must be changed if a key is lost or stolen.

Combination locks rely on people to keep the number secret. Any note of it should be kept elsewhere, preferably in a bank. Change the combination regularly or when a key holder leaves employment.

Card swipe systems are the most secure type of access control system. With a PIN system it's hard to monitor who knows the number. People can also be overlooked tapping it in. If you use a PIN system, change the number regularly.