First ill explain what a master key/rekey is and then ill explain how it can save you money and also give you more comfort and security.
A master rekey is when you want 2 keys to work on the specific doors, however one of the keys will only be able to access some of the doors (you decide which ones)
for example: you have a house and you want one key to open only the 2 side gates for the Gardner and pool guy, while your key (Master Key) will be able to open the side gates and all the locks in your home as well.
so that way you know your pool guy and Gardner can access the yard and the pool however have no access to your house.
A Grand master rekey is used more on commercial jobs vs residential jobs.
grand master rekey is when you want building "A" to have 1 key to open 2 of the doors and then you have another key that will open the other doors and then a master Rekey that will open all the doors in building "A".
Now you have Building "B" and you want 1 key to open 2 doors and another key to open the remaining doors and then a master rekey that will open all the doors in building "B"
A grand master Key will be able to open all the doors in building "A" and all the doors in Building "B"
so if you're the owner of building A and B and you dont want to carry 50-60 keys on you, it would be ideal to have 1 key that opens any door on your premises
if you have any questions or looking for a locksmith in corona to Rekey/change locks you can trust Keys and Locksmith corona with over 12 years of experience to help you with your locksmith needs.