The prop-n-lock was first designed in 2001 after working all night at several fast food restaurants. The stress of hearing "things" while working was not enjoyable. The first time I used it, I was amazed and how much safer I felt.
The prop-n-lock is used in many states and Canada for either the service companies safety or the store owners decision for their stores supplies.
After 5th generation changes, including powder coating verses anodizing and making the door claw clamp to zero, the prop-n-lock works on very many commercial doors.