Typical uses for door preps:
Cylindrical - cylindrical lever set or exit device with outside trim.
Mortise - mortise lever set or strike and flush bolt on paired door inactive.
Blank Reinforced - push / pull device or rim panic exit device
It is important to know the swing of a door, the hardware being used can be directly impacted.
With your back against the hinge side of the opening, pretend your arms are the door – left arm moves it is left hand, right arm moves it is right hand.
Now to complicate the matter:
Handing if based on standing on the outside of the opening. If you pull toward you from the outside, it becomes a reverse door. So that left hand door pulling toward you now becomes a right hand reverse and the right hand door pulling toward you becomes a left hand reverse door.
Still not sure, check out our handing charts