What were the factory grease pencil markings on the firewall for?

The marks on my `59
[IMG]http://i236.photobucket.com/albums/ff117/olddaze/photobucket-26445-1338846578849.jpg[/IMG]


1959 Shortbed stepside 1/2 ton project
[Linked Image from i236.photobucket.com]
[Linked Image from i236.photobucket.com]