Locking Horns used to be one of my least favorite techniques. But then I visited a school in Colorado where they didn't just check the attacker's right leg above then knee with the left hand---IF you can, then blast {at or above} the knee (instead of check it) as you step, then you can lock the knee joint and send the attacker backwards towards 12:00. There were a couple other minor varations to what I had learned (and I learned it pretty much like MJS's description) but I don't recall them. I think they were affiliated with Mr. Pick's organization.
Now, for me, it's not such a gosh awful technique.