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I'm not sure that asking this is against the rules but the feral ork rules are online so i was curious what the booby trap rule was for the trappas???
Not really supposed to answer ask/answer exact rules questions. The full rules are downloadable off GW online, i'd suggest going there to look. That will bring the least heat from the mods.
40K-Beakies(9-14-4),Guard(4-7-2),Orks(34-12-11). FANTASY-Dwarves(15-6-7),Beasts (14-14-1), Skaven (17-17-10) DoC (6-1-2). CYGNAR (28-15-1)
If they're anyway, they're in the Feral Ork list. I would give you a link but that area of the GW website seems to be down.
If not, then I don't know...possibly in the old Codex Catachans? that had something like Booby traps.