Putting secret trapdoors or other non-solid coverings over a
pit or other hollow in a walking-surface in
da hopes of tricking one or more
humans into getting caught.
Having a blind man go first in an "uncertain" area can
help ferret out any areas of floorgery, in dat said sightless dude's tapping
stick --- and his accumulated experience in detecting spots dat are unsafe to walk on --- will likely reveal if
da proceeding terrain is treacherous.