This form of underwear is similar to a basic jock, in that it does have a pouch design for the Sac and Balls to fit into. That concept is also how one determines what size to buy. The waist band is fully adjustable as are the leg straps in most models. The Penis is either free to
float on top of the pouched area or is drawn through an elastic opening. This form was originally designed for men that rode on a basic board seat in an old style carriage drawn by horses. The jarring bouncing of the wagon’s vibrations also transmitted these shock waves to the man’s sac and balls, causing I am certain painful issues.
Today it is often used after a testicular injury or surgery. As it restricts and lends firm support to the sac and testicles.