5.3.1.1 Conductor penetration through a shield
A shield has two surfaces, external and internal. If a conductor carrying interference
currents is connected to the outside of the shield, interference currents are confined
to the outside of the shield and have very little influence on the shield volume
enclosed. If the conductor is connected to the inside surface of the shield, all interference
currents are available inside the shield and may couple with circuits inside the
shield volume, which could potentially cause EMI.