How about this: Odd pickets get electrified on odd days, even pickets get electrified on even days. Just for shits 'n giggles, every once in awhile we electrify it all. Just for the hell of it and just to keep the hispanics guessing.
The pickets should be hollow. Drill a series of holes in each slat interconnect all the slats. Pressurize the interior with natural gas. Set the whole thing on fire. 30 foot tall 1000 mile long fence of flaming steel. That is a barrier