If anyone is wondering, everywhere the guide mentions "sheer force" and "sheer line", that should be "shear force" and "shear line". It's like "wind shear".
"Sheer" doesn't even make any sense in this context: "sheer force" would be twisting the tumbler so hard you break all the pins, and that would not exactly be considered "lock picking"!
What's interesting to me is how pervasive this misspelling has become. A Google search for "lock picking sheer force" finds 17,500,000 matches, but "lock picking shear force" finds only 205,000. I wonder if all these misspellings originated from this MIT guide, or if there was something else before that?