In reply to CantClimbTom:
> A second ascending a rope to recover an injured leader, down jumaring a rope to help an injured abseiler. Hauling a casualty up. All of these are - thankfully - exceptionally rare.
I don't entirely agree with this, I think the latter two are a bit more common. Taking away the injury aspect, I've had to jumar up a free-hanging abseil to rescue someone who was mid-abseil and I've had to haul a free-hanging person up a few times (a couple assisted, a couple not). I was also once in a situation where jumaring an ab rope with another person attached to me was a solution I seriously considered before deciding to do something else.
The list of problem-solving things sometimes seems endless. I mean, who would have thought that you'd have to work out how to turn an abseil into a tyrolean or lead out a pitch that was longer than your rope? How do you get out of dodge when the ab-rope is stuck and you only have a few metres of it on your stance? What if it's also hanging in space? It's amazing how bizarre and desperate the situation can become when things go wrong on a multipitch!
> But self rescue skills (which need periodic practice) are like airbags in your car. So far... I've never had an airbag deploy, but that doesn't mean I don't think they're useful to have, just in case.
I do a fair bit of wandering around with an ab rope looking at potential new crags - the sort of faff of rigging, abseiling, ascending, intermediate tie-offs, etc. etc. is a good way to get used to finding different solutions to move in different directions. Particularly if the wall is steep. It's not self-rescue per se but it's still useful and you get the experience while doing something else at the same time - if feels like less of a chore.