What must be done after moving the cut-out cock to the closed position?

After moving the cut-out cock to the closed position, it is crucial to bleed all air from the reservoirs to ensure that the system is operating effectively and safely. Closing the cut-out cock can trap air within the system, which can lead to pressure build-up or improper functioning of the air brakes. By bleeding the air, you eliminate any residual pressure that might interfere with the system's operation, ensuring that the brakes engage and operate correctly.

Additionally, this procedure is part of maintaining operational integrity and safety in rail operations, as it prevents potential malfunctions that could arise from trapped air. It ensures that the air brake system will respond appropriately when needed, contributing to the overall safety of the train.