I use katatedori as an offensive technique when confronted by knife. In the real world a man usually uses a knife to threaten rather than attack cold. To do this he must 'show' the knife and at this instant I teach the uke to become the aggeresor and grab the wrist holding the knife. It sounds odd but once you have trained to do it you can grab a wrist so fast and then atack nage(uke)'s center and do what ever.
After the students get competant to grab and hit it nearly every time I then change the mind set and tell them that they must attack by showing the knife and as uke/nage attacks their wrist they do the traditional techniqes. It works so very well. I have taught this series in seminars and workshops and I am always amazed how well people come to understand this attack.
BTW. I just came from ASU.ORG Congratulations.