A crotch rope can be either pleasurable or tortuous depending on the individual and how tight you tie it. They can work well as an element in predicament scenes, or as something that can be secretly worn under clothing out in public -- tied comfortably, one can provide gentle sexy stimulation to gradually get someone wound up over the course of hours (although this can also be tricky, as an unsexy segment of an adventure can easily flip that kind of thing from hot to irritating; be sure to make provisions to remove it in the field if necessary, i.e. carry some safety scissors with you).

One thing some people like to do is add "happy knots" -- generally a simple overhand knot, just to bulk up the crotchrope, positioned to provide extra stimulation to key areas. I don't honestly do this very often, because it's hard to get them to stay in the right spot, but it can be good for more short, intense scenes (as opposed to extended wear). On vulvas, it's particularly difficult to get the knot to stay right on the clit and often uncomfortable if you do; you may find over the vaginal opening to actually be a better spot. For people with penises, try aiming for the perineum.