Often certain portions of a circuit board need RF-tight shielding.
The following is a link to an article that appeared in EDN magazine
that describes the use of Hammond die-cast boxes and their tops to
shield a defined section both sides of a 2-layer board.
While the example shows a resistor bridging the ground trace through a
cutout in the box, RF circuitry may require a feedthrough capacitor
and a hole in the shielding box.
Here's the URL:
<
http://www.edn.com/article/CA379888.html?spacedesc=designideas&industryid=44217>
Regards,
Ted