An 18-inch steel plate which rests on the deck running the full length of the rails. Upon detecting an unauthorized weight on the rail (grappling hook, boarding ladder, hooked climbing pole, grasping fingers, etc), it raises on tracks to form a perfectly level, flush shelf on the top of the rail (think liftgate), thereby simply lifting the unauthorized climbing apparatus free to fall back from whence it came. It then immediately returns to deck level to prevent the pirates from opportunistically hooking the edge of the lift plate. To picture this, imagine one of those trucks with a liftgate.-- 21 Quest, Jan 31 2014 Wagon Wheel fence http://www.halfbake...gon_20Wheel_20FenceSimilar Art [AusCan531, Feb 01 2014] How does it tell the difference between a grappling hook and line being climbed by a skinny somali pirate, and being leaned on by a somewhat larger crew person?-- MechE, Jan 31 2014 by measuring the difference between the on-deck pressure and the on-rail pressure?-- not_morrison_rm, Feb 01 2014 I suppose it could be intergrated with some software in the ship's security camera system, or perhaps it could simply sound an alarm for someone to visually check that side of the ship and if needed they can activate it manually.-- 21 Quest, Feb 01 2014 Perhaps this system can be combined with vats of boiling oil...-- Grogster, Feb 01 2014 //combined with vats of boiling oil...
very poor batter-y joke narrowly avoided-- not_morrison_rm, Feb 01 2014 They are probably too busy knocking out furniture, but I suppose if they had workspace on board they could double-up.-- not_morrison_rm, Feb 01 2014 random, halfbakery