There are two components, the screw part and the dishonest
butler part. First you apply the screw to the cork, then insert
the d.b. around it. Now you have a three-point support that
should be sufficient to remove a cork, no matter how crumbly.
Here's the company take - from this you can see that the device
could conceivably be improved by making the parts interlock,
foolproofing the process for even the unsteadiest of hands.