Associated Locksmiths of America (ALOA) Practice Test 2025 – Your Comprehensive All-in-One Guide to Exam Excellence!

The keying rule applicable to GM locks is the concept of "maximum adjacent cut similarity" (MACS), which is a critical factor in ensuring key security and functionality. Specifically, a MACS of 2 means that no more than two adjacent cuts on a key should be the same. This rule helps prevent the creation of keys that could easily be duplicated by individuals who might have access to a partially similar key design.

Understanding the importance of MACS in key design emphasizes the need for varying depths and positions of the cuts on the key, which strengthens the overall security level of the locking mechanism. By maintaining a MACS limit, locksmiths can significantly reduce the risk of unauthorized access due to key duplication.

The other possible answers do not accurately represent the keying rules specific to GM locks. For example, the idea of the sum of key cut codes being a prime number or the first digit of the key code being even does not relate to established practices for GM locks. Therefore, the relevance of maintaining a MACS of 2 aligns with the industry's emphasis on key security protocols.