Why would searchlights in a prison or similar setting use a set pattern? [closed]

In numerous action/stealth movies, video games, cartoons, etc., they are escaping from a prison or similar setting, in the middle of the night when it’s dark, with the guards moving the searchlights in a predictable, set-in-stone pattern.
Continue reading Why would searchlights in a prison or similar setting use a set pattern? [closed]