In the article above, you’ll most likely read some very confusing double-talk about not using the Shunt for certain backup procedures, primarily in industrial situations.
My guess, without reading the whole ISO manual on it, is that it refers to a situation very similar to that used for backing up a toperope solo. I dug around in my Old Ropesolo Blog on Blogger but couldn’t find a picture to show you what I’m describing. I’ll see if I can take one later.
I have tried to let the shunt trail a bit lower, with some success, and there are some different schemes that you can come up with from digging around on the Petzl website, but if it doesn’t make sense, then it’s better to not get into it at all. Right?
Anyway, bottom line, from my own miserable understanding of the Petzl article, is if you think you’re falling, you don’t grab the rope, either above or below any device that auto-locks, like either of these. That could impede the locking function and cause you to fall. That could cause you to be injured severely. That could cause your heart to stop. Think about it long and hard. Please?