Yes, my bad. As for engineering degrees, you thread it the same way you thread a tube; there's nothing to it. If you somehow manage to thread it the wrong way (which seems impossible to me), you still have something with the friction of a tube-style device.

Warning: it ain't cheap, small, or light. You're basically getting a gri-gri for double ropes (except that it handles better than a gri-gri in my opinion). Looking at picture isn't going to help, you really have to try it out to see how much better than most other devices it is.

Here's a link to the Rock and Snow page, which, I think, simply repeats the manufacturer's blurb.