Crotch rope
From wipipedia.org

A crotch rope (Sakuranbo) is a bondage rope harness tied around the hips and groin.
In Japanese bondage a crotch rope is tied in such a way as to rub against the genitals. The aim is to generate thoughts of sexual submission and excitement in the person thus tied.
The same purpose may exist for Western-style bondage, which also uses them for anchorage when restraining a victim or support during suspension bondage or on a St. Andrew's cross.
Crotch ropes appear regularly in the drawings of Robert Bishop.