What are the benefits of a master key?

Master keys are especially beneficial for businesses. Employees can have differing access to parts of the business. For example, the owner will have access to everything, but the manager may only have access to some areas. 

Do I want the locks on my home to be keyed differently?

Unless you have a specific reason (limiting entrance of children, maids, etc.), having the locks on your home keyed differently can be very inconvenient.

How can I practice key control?

There are high security locks that require keys that cannot be reproduced by anyone without the direct permission of the owner of the lock. 

Should I invest in locks that promise higher security?

The material in which the lock is made from can make a big difference. If you can afford to invest in a lock that is made of superior material, you should definitely look into it! In most cases, they are not even that much more expensive.