They Inc. Are well known in our metro as the manufacturers of high security locks and alarms. Their mortise deadlocks are found on many apartment doors. They are expensive, but you are paying for the service: they take security seriously. They take details (address, name) of every property to which they fit a lock, and will only provide spare keys or extra keys if you can provide evidence that you are the legal owner. I have also bought window locks and sliding door locks through their technician (they have a good range of general door and window fittings) and sought advice on security from them. When they get around to you it is always personal and helpful.