extremesanity

I have 10 doors in my warehouse. On many of them, due to position/space constraints, I am unable to point a camera at them. We currently have some cheap dome cams setup high above the doors, that are successful in only capturing a fuzzy picture of the top of peoples heads. I thought of doing a wall mount box cam, but it seems like a person could easily slide around it in some situations. How can I place a camera to catch a persons face leaving through the door 100% of the time?