Crotch Rope Walk

It is a BDSM practice in which a length of rope is pulled relatively tight and fastened across the room at waist height. Then the (usually female) submissive is to put the rope in between her legs and to start walking slowly. The rope bites into her private parts, causing pain and/or pleasure, depending on the preparation taken. The rope might have knots in regular or irregular intervals to intensify the sensation.

An alternative version is when the submissive partner remains stationary and the rope is pulled between her legs.

NSFW Exmaple 1, NSFW Example 2