University stickers on the parking lot crossbeam

This clip is from The University of Michigan’s University Hospital. So whenever someone enters the hospital, he/she gets a sticker at the front desk indicating that the individual has a valid appointment. And when the individual leaves the hospital the sticker is then useless. So you can see that people put their stickers on the crossbeams on the ceiling of the parking lot on their way out - and only one side of the crossbeams is filled with sticker.