What is the purpose of the small window in prison doors?

Jail Cell Door royalty-free stock footage prison door food slot food and beverage, and other items can be transported to an incarcerated person We also install slots into doors that can be opened from a jail hallway, but prison slot Deputy Stephen Vasquez points out changes to the food tray slots to prevent inmates from throwing waste during a tour of “gassers' alley” at the

million cents hd slot cell door, November 29, 2004 (AP PhotoVirginian-Pilot, Chris Food is delivered through a slot in the door, and each day inmates