You'd place the waist harness (attached to the ropes) around the victim and then slowly lower him/her onto the pyramid shaped seat with the pointy top inserted into their anus or vagina. With the downward pressure caused by the victim's body, the muscles around the orifice would eventually tear thereby impaling the victim. It was also called the nightwatch because when pressure is applied to certain parts of the body, the person cannot fall asleep.
