The lock upgrade option will replace the standard lock installed.  Additional locks on the other drawers are optional.  If you want independent control of each drawer, you will need to buy additional 3 locks if you have a 4 drawer cabinet.  If you buy only 1 additional lock, that drawer will still be dependent on the top lock.

You can purchase multiple locks by adding this item to your cart multiple times with different configurations.

The lock upgrade option will replace the standard lock installed.  Additional locks on the other drawers are optional.  Cabinets will arrive with the lock options pre-installed.