After the shingle is cut, he sticks them in the slot where a big wheel is spinning at a slower speed, that has several planer knives, I think there are four, 1/4" thick, about 3" wide, 6" long, that's what squares up the shingle. When he gets into good wood, shingles are really coming of that fast and furious, around 5-6 square a day.
Two years ago he found out just how sharp that saw is, in a split second, lost part of his trigger finger, he wasn't sure what happen but think he got complacent, it's definitely a pay attention job.