What does "double-checking" refer to in air brake inspections?

Double-checking in air brake inspections involves confirming that all components are functioning properly after a visual check. This process is crucial for ensuring the safety and reliability of the air brake system. After the initial inspection, which may include checking for obvious issues, double-checking allows the inspector to verify that there are no hidden problems that could affect the performance of the brakes. This might include ensuring proper connections and functionality of components like valves, cylinders, and brake shoes. By taking the time to double-check, inspectors can identify any potential malfunctions that might not have been immediately apparent, significantly enhancing the overall safety of the rail operation.