Oh man, I gotta push back a little here. The chalk line isn't optional but I wouldn't blame the kid 100% for forgetting his box. We all do that at least once. The real issue is him not going back to the truck to get it. That's just laziness or inexperience. Snapping a line takes no time at all and it saves so much hassle. I taught my apprentice that lesson the hard way by making him redo a whole wall that was off by 3/4 inch. He never forgot his chalk box again. You gotta respect the tools that keep everything straight and true.