Homebrew PCBs

Hi all,

I have been looking at some board from some other stuff, laser jets 
I've pulled apart and alarm panels and stuff, and I have seen more 
than a few sections near terminal connections that look like 
triangles in a row, and a mirror image so the very tips of the 
triangles seem to touch.

any idea why ?
and is one does them (for the reason in the response) is there a real 
need for them ?

Dave