Developing Floor Master Keys Within Existing Master Key Systems

Two different methods can be applied to develop sub-master keys within an existing master key system: a traditional method and the unconventional “guerilla” approach, designed to get maximum results from minimum resources.

Locksmiths are often called out to rekey areas where an existing master key system is in place. Many times records relating to these systems are outdated, unclear, or incomplete. When starting a new master key system is out of the question, it is up to the locksmith to either pass on the job...

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In Figure 5, these cuts are recorded (in black). The cut entered was a 4 in the second column.

After examining third floor change keys, there was nothing new to add to the KBA but all third floor change keys had the first, fifth, and sixth cuts in common with the third floor master: 7 _ _ _ 5 0.

At this point, all keys have been either gauged or callipered.

The customer has verified that there were no other types of keys used.

The empty cells in the KBA can be filled in and used to develop key combinations that were never used and therefore safe to use.

The rest of the cells in the KBA will be filled in with a red marker to later identify what was added. The numbers will be select using proper master key procedures. Each column in a two-progression bitting array will use either the subset of numbers: {0,2,4,6,8} or {1,3,5,7,9}.

In Figure 6, the rest of the KBA is filled in. The KBA is almost completed all that is needed is to enter the sequence of progression. This is important as it shows which column will progress first.

When reviewing the change keys for each floor, it looked like the second, third, and fourth cuts differed and was used to generate the changes under the floor master. Two cuts in the second column were filled in as new. Because these columns are used to generate change keys, they were designated as: 3, 1, and 2 sequences.

It is noted that the cut that distinguished the difference between floor masters was in the fifth position; therefore that column will receive a number 4 sequence.

The remaining columns (first and sixth) will be designated either 5 or 6. There isn't much that can be determined to their original intent so the columns will be arbitrarily designated 5 and 6 (rather than 6 and 5).

The sequence will be entered (in red) into the KBA as: 5 3 1 2 4 6

Getting back to the first part of the request, rekeying several areas on the second floor, the completed KBA can be useful to obtain “fresh” key combinations that have never been used.

All second floor change keys will have the first, fifth, and sixth cuts in common with the second floor master: 701870. To guarantee that change keys have never been used, each change key generated must have at least one “red” cut from the second column.

In Figure 8, all the new key bittings are listed. Note they make use of the red numbers in the second column of the KBA.

The second part of the request is to generate a new master key for the third floor and to rekey all areas on the third floor. The first, second and third floor masters are: 701810, 701870, and 701850. The next key in progression and one that uses a new (in red) cut is: 701830.

To generate more floor masters, progress keys in the next sequential column (sequence 5). That is the first column. Figure 9 progresses other possible floor masters using this column in the KBA.

This method gets the job done but gauging keys can be tedious and time-intensive.


“Guerilla” Method

The method is called “guerilla” because it is unconventional, designed to get maximum results from minimum resources. All that is needed is the TMK.

Twenty-four “diagnostic” keys are cut based upon the key bitting of the TMK: 501892. The diagnostic keys are grouped into six sets; one set for each pin stack in the lock cylinder. Each set includes four keys; each key tests a cut in a chamber.

For example, the first cut of the TMK is 5. Standard master key practice dictates that if a 5 is used as a TMK cut, the other cuts in that position must be either: 1, 3, 7, 9. Each of the keys in the first set of diagnostic keys will have all cuts in common with the TMK except for the first cut.

The cuts of each key in the first set of diagnostic keys are: 701892, 101892, 301892, and 901892.

Each key in the first set will be stamped with two numbers: the first is a 1 representing the chamber it is used for and the second the change cut for which it is testing. The keys are in the first set would relatively be stamped: 17, 11, 13, and 19.

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