Of the following locks, which one type is generally considered to have the poorest security value?

The choice of key locks as having the poorest security value is based on several factors regarding their susceptibility to unauthorized access. Key locks can vary widely in their security, but standard pin tumbler locks, which are quite common, often have vulnerabilities that can be exploited by various techniques, such as picking or bumping.

In contrast, interchangeable core systems offer greater flexibility and can be upgraded or rekeyed without removing the lock cylinder, enhancing their security when managed properly. Conventional combination locks rely on a numerical code, which may be more secure than traditional key locks in some situations but can still fall victim to brute force attacks or code guessing.

Manipulation-resistant combination locks represent a more advanced level of security, as they incorporate features specifically designed to resist unauthorized manipulation. They are engineered to prevent attacks that exploit weaknesses found in simpler locking mechanisms, such as standard key locks.

Therefore, while all locks have their place in a security program, the basic key locks, particularly the standard models, generally lack the advanced protective features found in the other types listed, thus making them less secure overall.