i guessed the idea was to back up a pick-up truck and dump a dead animal out of the bed onto the dirt between the a-frames , and then to tie ropes to the animal 's hind legs , and then to flip the ropes up over the top rail , and then to use muscle power or the pick-up itself to haul the animal up in the air so that it hung vertically and upside down , ready for the butcher 's knife .