As a blog author and locksmith, as a business owner and statistician, I keenly watch the results using Google Analytics, of the search terms people use while attempting to gather knowledge that may help them to be more aware when purchasing products or services.
I am noticing a significant number of searches recently about master keying although, it may be due to a cardinal lack of understanding about the principle.
It seems that many searches recently are from people who assume that all deadbolts are master keyed. This is simply not true. It is a fallacy.
A deadbolt, or any other lock for that matter, must be purposely master keyed.
There are no pre-fabricated master keys for residential or commercial deadbolt locks.
In bygone years, manufacturers of some bit-key type mortise deadlocks, did produce some of their ranges with a purposely designed flaw allowing for a "skeleton" key to operate. This skeleton key was often referred to as a Master Key.
There are some manufacturers of coin machine locks or cam locks, that routinely produce their locks to be master keyed. The primary benefit in using master keyed coin or cam locks is for commercial situations like an office complex that uses on-site maintenance to minimize the quantity of keys a janitor or other service person can be required to carry.