There was a discussion on the CM forum about the prong collar, and there
were some interesting "points", about that type of collar vs others,
especially as to their relative safety and effectiveness for training loose
leash walking and heeling, and for correcting pulling.

http://community.sessionswithcesar.c...s/t/33888.aspx

I have no problem using the prong collar on Muttley, and I realize that the
prongs are not meant so much to inflict pain or injury as they are to
provide a "pinch" to the neck as a correction and redirection of focus. But
I wondered if it would seem more humane and also be effective to reverse the
collar with the prongs facing out. Hence the name "GNORP". Here's the
result:

http://www.youtube.com/user/PaulAndM.../6/MxYHWF1SQkY

From what I've read and personally experienced, the prong collar is actually
the least potentially injurious device for training as well as emergency
control, and by reversing it perhaps it is even better. Ideally the dog
should respond to the distinctive sound of a collar pop on the chain, and
the outward position of the prongs can even provide protection from attack
similar to the pronged collars worn by Anatolian Shepherds in Turkey where
they protect sheep from wolves.

http://www.cobankopegi.com/collar.html
http://www.cobankopegi.com/prong.html

Paul and Muttley