Five Stars if you dig your Rutschblocks in nice powder.
One Star if you dig in an "Arctic Maritime" avalanche climate.
(And of course no stars if you no longer dig them given the extensive time requirement and the dubious advantages relative to the PST and ECT ... although when you're teaching an avy course, having a student gingerly step onto the block is kind of the money shot for the entire course, so I suppose they still have a place even just for photogenic purposes.)
In theory, you can use this cord to isolate the block just by placing a probe at each far end: you and your partner saw back & forth then progressively downward.
In reality, don't even think about doing this with carbon fiber probes, and even an alu probe will immediately become very scratched.
If your snowpack has any crust layers, then forget about isolating the back of the block sufficiently this way.
However, if you do "chimney" out the sides completely, then you could use this for some sawing in back (with you and your partner standing at each far end). But this probably still won't isolate the back completely.
On the plus side, but the design is rather clever, and it appears solidly made, so overall way better than attempting the same thing with your own knotted cord, and perhaps you can come up with other applications for it.
Multi-use gear is bonus for ultralight enthusiasts and G3 offers one with the Rutschblock cord. The coated steel cable is designed for isolating snow columns but is also great cutting small cornices. No need to carry dynamite and a snowpack tool, just carry the G3 Rutschblock cord. The cord is dotted with stiff metal springs that create slicing friction while you saw like a lumberjack. The kit comes with a stuff sack to keep your pack nice and tidy while you make a mess of the slopes below.
Update 2020/21: G3 changed the color of the bag from grey to red but otherwise the product is the same.
