Why do these safety instructions have a ruler on them? I was on a Wizz Air flight the other day and the safety instructions leaflet had a CM ruler running down the side of it.

What is the purpose of this?
This looks like just a courtesy tool on the safety card, but doesn't actually have a requirement or purpose. Previous versions of their safety card did not have this courtesy tool.


(Image Source: aviationfreaks.freeforums.org)