The post defining cast-off and can't by Kutter, along with the photos posted by LRF make this explanation about as idiot-proof as anything I have seen. Since the subject comes up from time to time, it would be nice if Dave saved those two posts as a Sticky in the FAQ section, for future reference.

This subject, and much more, is also very well covered and explained in the book "Gunfitting: The Quest for Perfection for Shotguns and Rifles" by Michael Yardley.

A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.