What is one of the key features of the hammer at half-cock safety?

The hammer at half-cock safety is designed to provide an additional layer of safety when handling a firearm. When the hammer is in the half-cock position, it is not fully engaged to strike the firing pin, which significantly reduces the risk of accidental discharge. In this position, the mechanism locks the trigger, preventing it from being pulled and thus ensuring that the firearm cannot be discharged unintentionally. This feature is particularly important during periods of handling or transporting the firearm, where there is a risk of it being dropped or jostled.

In contrast, other options describe functions that would either increase the possibility of an accidental discharge or inadequately secure the firearm. For example, if the hammer rested on the firing pin, it could potentially fire if the firearm was dropped. Similarly, having an unlocked trigger or disengaged safety would compromise the firearm's safe operation, increasing the risk of accidental shots. Therefore, the functionality of the half-cock position as a means to lock the trigger is a crucial safety feature in firearms.