Which item serves as a retention device to prevent accidental disengagement in assemblies?

The cotter pin is specifically designed to act as a retention device in various mechanical assemblies. It functions by securing other components in place, preventing them from loosening or disengaging unintentionally. When inserted through a hole in a bolt or shaft and bent at the ends, the cotter pin creates a secure locking mechanism that holds the assembly together under tension or vibration. This is particularly important in applications where safety and reliability are critical, such as in aviation or military operations. While other devices like a locknut or drilled bolt may provide stability or facilitate locking mechanisms, the cotter pin is uniquely effective in directly preventing accidental disengagement of connected parts.