Example No. 1: Consider three master key systems (three levels each), whose TMKs are A, B and C. Here are the bittings of each grand master key: Figure 1. These are the three grand master keys: A, B and C. 5 4 5 6 1 2 A 7 4 5 6 1 2 B 1 4 5 6 1 2 C To make this work, all three systems will have a fixed constant in the first position. Remember, a constant is a place where the change key has the same cut as the TMK, and the lock has no master pin in that chamber. ANSI/BHMA A156.28 subsection 5.3 tells us to use as few master pins as possible, which means more constants. Constants are your friends. Constants can rotate, or they can be fixed. I said the first position is a fixed constant in all three systems. That means all the keys in the A system (including grand master A itself) have a 5 cut in the first position, and none of the B or C keys have a 5 cut in the first position. Similarly, all the B keys have a 7 cut in the first position, and all the C keys have a 1 in the first position. We have effectively isolated A, B and C from each other. Here’s a way to visualize this. Imagine three castles, each run by their own lord. Lord Anthrax has total authority inside Castle Anthrax, but no authority at all outside the castle walls. What happens inside the walls is of no concern to the lords of the other castles. But this depends on three important principles. First, all the lords must agree to respect the castle walls. Sec- ond, it must be absolutely clear where the walls are. Third, no one is allowed to live in more than one castle at the same time. Figure 2. Here are the three lords of three castles. A 5 4 5 6 1 2 Lord Anthrax B 7 4 5 6 1 2 Lord Belvedere C 1 4 5 6 1 2 Lord Cadbury How many total constants are in each master key system? We don’t know! The technique of building brick walls makes no assumptions about constants inside each castle. We’ll come back to this idea later. Suppose we want our three grand master keys under a great grand master key, making one big four-level system. Now the three castles are unified under the benevolent rule of Queen Gertrude the Great. Figure 3. Here are three "lords" and a "queen." GGM 3 4 5 6 1 2 Queen Gertrude the Great A 5 4 5 6 1 2 Lord Anthrax B 7 4 5 6 1 2 Lord Belvedere C 1 4 5 6 1 2 Lord Cadbury To make this happen, we need to put master pins in the first chamber of each lock. Technically, that means the first chamber isn’t a constant anymore. In the first position, an A key must have the same cut as the A grand master, but different from the GGM. I hope this is clear. We made a rule that all the A keys have a 5 cut in the first position, and we must stick with that rule. That is the brick wall around Castle Anthrax. Are the three castles still isolated from each other? Each lock under the A grand master is pinned to an A key (which has a 5 cut in the first position) and the GGM (which has a 3 cut in the first position). Hence, every single one of the A locks has a 3 bottom pin and a 2 master pin in the first chamber. None of the B or C keys have the right cuts to operate that chamber. The B keys all have a 7 cut, and the C keys all have a 1 cut. Conversely, consider a lock from somewhere else in the sys- tem, not under A. We know that the first cut on its change key is something other than a 5, so an A key won’t have the right cut to operate that chamber. Remember, this depends on our agreement to respect the castle walls. For example, we will not attempt to use an incidental master key that has a 5 cut in the first position because that key would straddle more than one castle, crossing the walls. Next, I want to show you a different example in standard pro- gression format (SPF). Example No. 2 shows a page of 64 keys. They are organized into four keys in a block, four blocks in a ver- tical group and four vertical groups on a page. The block masters are highlighted in orange, and the vertical group masters are highlighted in blue. The system has three fixed constants, as we can see from the key bitting array (KBA) in the upper left corner. WWW.ALOA.ORG JANUARY 2024 KEYNOTES 41
