Piggie

If you do any ready and you may have on reflector specifications for screen reflectors be in a yagi, bowtie or even building a dish for VHF, UHF or microwave. Good example of a dish on UHF is the old CM4251.

Remember any mesh screen where the holes (spaces between the metal) are less than 0.1 wavelengths the radio wave sees this as a solid piece of metal. This can be seen in many ways. Simplest might be just the effect of the metal being that close to the wave. It can also be shown considering the radio signal as particles and not waves. This gets bizarre to think about since it doesn't make any sense. It would seem if light photons were very small they would go through anything wider than them. This can be shown with the classic 2 slit experiment where light appears behind the slits in a place where there isn't a slit (same theory as slot antennas). Well they appear in a place between the slits because it is a wave and a particle at the same time. If you think about this, it's really even more bizarre. The particles in the 2 slit experiment not only go through the slit as expected but as above also appear between the slits. This means the particle is in two places at the same time.
Double-slit experiment - Wikipedia, the free encyclopedia
Classic Two-Slit Experiment

So even though can shoot a bullet between the metal in a mess reflector the waves won't penetrate it.

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So what is 1/10 of a wavelength at common TV frequencies? These are approx for example

Lowband 18 inches
Highband 6 inches
UHF 2 inches.

So to block a UHF TV station from entering the house one would have to put a wire or some piece of metal every 2 inches both horizontally and vertically, so that no area of the wall had a gap of more than 2 inches if wishing to reject both horizontal and vertical waves. As you can see houses aren't built that way unless they have solid metal walls or roofs. UHF gets through windows and walls. Even metal studs are not close enough together to stop UHF.

On highband metal studs in the walls spaced on 18 inches would not be a perfect reflector, they are spaces at 3/10 of a wave length, giving a great deal of blockage. As you can then see low band really has a hard time finding a hole large enough to get in, unless the house is soley wooden and little wires in the walls.

There is the large and small of it.