What is rope walk?
Japanese crotch rope walk is a BDSM technique in which a female slave is made to walk along a (usually knotted) rope threaded between her labia and buttocks.
Hardcore rope walk
Other rope-like objects like chains or cables can also be used in more hardcore bdsm play.
Adding other elements such as pulleys, can make it even more hardcore and are used by experimented bdsm masters as a perfect way to punish their slaves. Even an automated method can be used, althought it could hardly be called “rope walk”.
Self play
Rope walk can also be done without a master, as self bondage. The ropes would probably be not as tight, but it definitely looks like a fun thing to try.