If you own a warehouse in a bad part of town, people at some point might try to get into it. They usually attempt brute force attacks like hammering the lever or deadbolt off of the wall, or twisting the lever as hard as they can until a small part breaks inside which is why you should spend a little more to get a clutched lever. If they are slightly more sophisticated, they may attempt to open the door by attacking the latch mechanism of your lever with a screwdriver or a sawzall or hacksaw or something of that nature. This can easily be guarded against with the addition of a latch protector.
Latch protectors come in different sizes and types. Some are meant for residential applications and some are for commercial. The commercial ones tend to be big ugly pieces of metal, but they also have different features that make them more useful, like a prong that goes into the door frame to prevent a criminal prying the protector back.
I take no responsibility for what you do with the following information:
They are easy to install. Two holes in the door in the correct place is usually all that is necessary, and maybe one or two holes on the frame next to the door if there are prongs to prevent prying on the protector. Don’t drill the prong holes too big or they won’t work and the protector can be pried just as well as if the prongs weren’t there at all. If you don’t want to chance drilling the wrong place or installing it wrong, give me a call and I can install one very cheaply for you. They only cost $20, installation only costs $25 on most doors, and my service call is only $65. You can have peace of mind for $110! (My prices already include tax)