method that was used by the Vietcong during the Vietnam
War was a simple pit in which
punji sticks were
placed in the sides, pointing somewhat downward at an
angle, thus trapping any victim that walked into it and
making it near impossible to quickly free the victim or
without causing even greater injuries. A metal cage with
downward pointing pins, based on the same principle –but
quicker to deploy– also existed.
See THAILAND'S NEIGHBOURS & BEYOND.