My thoughts regarding the special locking features so far .
I think the half locked up position locks the main horizontal bolt works
that's Controlled by the outside turn handle mech
There's a few kinds on chubbs custodial site And I've included a few pics of them
ie. The main locking bolt to secure cell door Mechanism 4L65 4L55 4L56
So locks the bolt back every time inside of the door ..even when open !
all that's needed is a Double notched horizontal main bolt and you've got a secure
Anti-tamper proof bolt mechanism that stays locked all the time
Otherwise when the door is open a inmate could potentially gain acces to this
Bolt by a twist of the out side handle and over time Saw it Off or weaken it
Going unnoticed By authorities.
Then with a good blow the bolt ...would break off and it would fail
The lever cell lock bolt is forced by the springs to the half way locked up position After a opening
Every time by itself ..it can not be over looked by the key holder.
The brass side arm stops the bolt at the half way position as it's under spring tension
As the bolt travels downwards with some force ..the arm buffers and stops it from becoming overshot.
A very good security feature to have .. and the inmate never gets to see the bolt in door
Ringo