Positional multiplex keyway system

In a lock-and-key system that includes a first lock-and-key family comprising a plurality of differently-bitted first keys each having a first profile and a corresponding plurality of first locks each operable by a corresponding one of said first keys and each having a first keyway configured to accept said first key profile for entry of said first keys into said first keyways, wherein said first key profile comprises a first key section that extends between a base having a width and a top bitting surface and a predetermined contour defined by a groove extending along said first key section at a predetermined spacing above said first key base, and wherein said first keyway has a profile complementary to said first key profile and comprises a blocking element disposed for complementary mating engagement with the first key groove when the first key is disposed in said first keyway, the improvement comprising a second lock-and-key family, said second family comprising:

• a plurality of second locks each having a second keyway;
• and
• a plurality of differently-bitted second keys each having a second profile and each bitted for operating a corresponding one of said second locks;
• wherein said second keyway is configured so that each of said first locks and each of said second locks can be entered through the respective first and second keyways by a single master key for operating all of said first and second locks;
• wherein said second key profile comprises a core section configured as said first key profile and a narrowed projection extending from said first key profile base of said core section in a direction away from the core section and opposite from the top bitting surface and having a width less than said first key base width such that said second key cannot enter the first keyway of said first locks;
• and
• wherein said second keyway is configured for receipt of said second key profile and includes a foot for accommodating said second key projection and a blocking element for complementary mating engagement with a groove defined in said second key core section when the second key enters the second keyway and for complementary mating engagement with said first key groove when the first key enters the second keyway so that said first key is receivable in said second keyway.

In a lock-and-key system comprising a plurality of differently-bitted first keys each having a first profile and a corresponding plurality of first locks each operable by a corresponding one of said first keys and each having a first keyway configured to accept said first key profile for entry of said first keys into said first keyways, wherein said first key profile comprises a first key section that extends between a base having a width and a top bitting surface and a predetermined contour defined by a groove extending along said first key section at a predetermined spacing above said first key base, and wherein said first keyway has a profile complementary to said first key profile and comprises a blocking element disposed for complementary mating engagement with the first key groove when the first key is disposed in said first keyway, the improvement comprising a method of providing a plurality of second locks each having a second keyway for use with a plurality of differently-bitted second keys each having a second profile complimentary to a profile of the second keyway and each bitted for operating a corresponding one of said second locks, said second keyway being configured so that each of said first locks and each of said second locks can be entered through the respective first and second keyways by a single master key distinct from said first and second keys for operating all of said first and second locks, said method comprising configuring the second profile of the second keyway as comprising a core section configured complimentary to said first key profile and a narrowed foot recess extending from said core section in a direction away from said core section and opposite from said top bitting surface to a baseline of the second keyway, said narrowed foot having a width less than said first key base width, for receipt by said second keyway of the complimentary second key profile and for receipt by said second keyway of the first key in a position in which the first key enters the complimentary core section of the second keyway and is unable to enter the narrowed foot of the second keyway and is thereby elevated in the second keyway above the second keyway baseline to prevent operation of the second lock by the first key.