Thanks to all for your replies. I have two sources of information. The NRA diagram book and Walt Snyder's book on the Ithaca Gun Company.

In my post I was not clear. My Knick 4E FE is not loose. What is loose is my understanding of the FE lockup function on this SBT. Ithaca5e FE explanation helped a good deal. I have no intention of turning a screw.