[rightwinggoth]

make another one parallel behind it. and put a trench in between.

[IM2MAD]

make another one parallel behind it. and put a trench in between.

And fill the trench with alligators.

[Desron13]

"make another one parallel behind it. and put a trench in between."

I was thinking more along the line of evenly spaced Claymore mines rigged with motion detectors. Problem solved!