Master Keying


This is something of a confusing subject to cover as there are Master ® brand locks, yet also keys referred to as ‘master keys’. So first, some disambiguation:
Keyed alike vs. master keyed:
-A master keyed lock can be operated by two or more keys which are NOT cut the same.
-Two or more locks which can be operated by a single key (or multiple identical copies of a key) are said to be keyed alike, not master keyed.
So while it may seem like your house key, which (hopefully) operates every lock in your home is the same as the master key the custodian at the school carries, since his key also operates every lock in the school, it’s quite different.
It’s easiest to explain this if you consider a key to be a password. A lock which is master keyed has more than one password programmed into it, i.e. more than one unique key will operate it. If multiple locks all have the same password programmed into them, but only ONE password, they’re keyed alike.
As locks are simple machines rather than complex computers, the number of available “passwords” is mathematically small. Using a 5 pin key with 6 unique depths (both common values for residential or light commercial locks) yields 6^5 or 7776 possibilities, but that number is cut in half once impossible-to-cut or undesirable combinations are eliminated. A far cry from the typical password requirements even the most unsecure website would require. . . but odds are nobody is planning to cut 3,000 keys and attempt a brute force attack on your home or business.
Regardless, because of the mechanical and mathematical limits imposed, master keying is best done as an engineered system (the alternative being a “shoebox” master key system where random change keys are used in a completely uncontrolled manner, which causes lots of problems).
So when should you consider master-keying? When you need to grant access selectively to one or more locks to certain keyholders, but want the convenience of a single key for yourself or other (hopefully trustworthy) persons.
An example for homeowners might be adding a “yard guy key” to an exterior garage door or storage shed. The key you carry will operate it along with all of the other doors in your home, but your ‘yard guy key’ will only operate the doors you specify.
For businesses/commercial facilities, master key systems are typically much more complex and beyond the scope of what can be described in a little article for our website. Call or email us to discuss a customized solution for your facility.
• The locks on my commercial building are a mess. I’d like to get a master key system in place. How much does this cost?
Before we can answer that question, we’d need to do a site survey. This involves walking the property and tagging each door, assigning it a number, and documenting what hardware is currently installed and evaluating it’s condition. Once that’s done we  determine what hardware can stay and what needs to be replaced (to eliminate incompatible keyways, worn-out locks, code violations, etc.) and create a materials list and estimate from that. This can take several hours, depending on the size of the facility.
We do charge a modest fee for the site survey, but we will provide the materials list and door survey with markups to you upon completion regardless of if you accept our estimate. This will be useful (essential, really) for any other bidders from whom you may wish to seek estimates. If you hire us for the job, we credit what you’ve paid for the survey against the final invoice.
We do offer no-charge estimates for this service, but those are limited to providing flat pricing for hourly labor, trip charges, per cylinder charge for master keying, and materials costs for keys, locks, cylinders, etc.
• Ok, I got your estimate and I like the price. What’s next?
Once approved, and with your door survey complete and in hand, we will discuss how you’d like our system to operate (which keys should operate which doors). We do this with a keying matrix, which is a spreadsheet with doors listed in the rows and keys along the columns. If a key operates a door, the intersection on the spreadsheet is shaded.

We generally provide a blank keying matrix (doors will be filled in and some keys may be labeled but no shading done) for you to fill out and return to us, but in some cases if we feel like we understand what you’re looking for, we may fill it out for you and submit it for approval. Either way, once it’s been approved, we start doing the boring and tedious math to make it all work. The keying matrix is generally exchanged via email as it’s easiest and difficult for either of us to lose.
With the matrix complete and approved, the last step which requires interaction on your part is to let us know how many copies of each type of key will be required (copies can always be made, but we like to make sure you’ll have enough to circulate). We retain one copy of each type of key to facilitate install and testing.
Next, we cut keys and build any locks or cylinders we can in-shop prior to install date. Once the keys are done, we can (and generally do) turn them over to you for distribution prior to installing the system at your facility, thus making the transition as seamless as possible.
Final step occurs on install day. . . which is just as you might expect. We show up with keys, plans, and cylinders in hand ready to roll out your new system. As we’ve done as much work as we can behind the scenes, this last step is usually pretty fast and relatively painless to you. Any locks that are deemed to be in acceptable condition are disassembled and rekeyed on site, replacement locks or cylinders are installed on those that aren’t, and everything is tested once install is complete.
Once the install is approved by you, we provide you with our master keying records (which allows you to have the system serviced by any qualified locksmith, but really, at this point why would you not continue to use us? We’re awesome), finalized keying matrix and door survey chart, and (our favorite part) our invoice.
• I need to add or change some locks in an existing master key system. . can you do this?
If we designed your system, no problem. We retain records for all master key systems we create, and provide them to the end user at no charge upon completion of the project.
If the system was designed/installed by others and up-to-date and accurate master key charts or a bitting list is available, yes. If not, we cannot expand a system without reverse engineering     the existing system to determine if expansion is even possible. Constructing a master key chart or bitting list by reverse engineering typically requires a measuring and documenting every change key in use in the system and may require disassembly of some of the locks to measure and decode pin stacks. This is costly and time consuming but it can be done.
Expanding a master key system without this information is on par with adding an extra story to a building without knowing what the foundation can support. It’s dangerous and a violation of locksmith licensing law here in TN so we don’t do it. An alternative to reverse engineering is to simply abandon the existing system and engineer a new one. It can be applied in stages if the budget is tight, provided you don’t mind carrying 2 master keys.
• I lost my master key. Can you deactivate it without rekeying all the locks?
Unfortunately no. If a key is compromised, every lock it operates must be rekeyed in order to secure the system. For this reason we strongly recommend issuing master keys only to essential personnel and only with a strict key control policy. Electronic Access Control is an excellent solution to frequent rekeys if keyholder turnover is a problem for you. Call or email us to discuss a customized solution.
Lock Medic

123 W. Broadway St.
Lenoir City, Tn 37771

M-F 8:30am to 5pm
Emergency number: 865-986-0020