A brass pillar cock is a toy that can be used in place of a strap-on dildo. It is typically a hollow tube that is secured to a base and has a screw or cap at one end that is used to tighten the tube to the base. It is usually designed with a thin ring or loop of metal around the outside of the tube to hold a small vibrator or dildo. The rings can be removed and replaced with others to change the toys appearance and size.