Metal materials can not be radiation, shielding radiation can not fly.Have you ever heard of absorbing materials? Previously used in the military, can be considered, absorbing materials can absorb electromagnetic radiation,Heat energy dissipation.
For example, the wavelength of 1GHz is 0.3m, then the hole is less than 0.3/20=1.5cm can be a good shield (that is, no electromagnetic leakage).
In general engineering, the electromagnetic leakage of the hole is /20
