With this mod, you can channel your inner thief and non-lethally take down guards in stealth. Doing so will prevent the guard's pager from going off and it will not register as a kill on the ending stats screen.
To properly knock out a guard, the following conditions must be met:
You must attack him with a melee weapon
That melee weapon must be of the blunt type, so no knifes or machetes (as a general rule, if a melee weapon has a higher base knockdown than its base damage, then it will qualify)
You must be behind the guard
You must hit him before he detects you
The strike must hit the guard's head
Since you can't stuff unconscious guards into bodybags, any guards you knock out cannot be bagged. If you knock them out on a well-travelled route then they will be spotted. This can be disabled in the options menu, but doing so will also re-enable pagers.