On rare occasions when a new screw length or width was needed, an engineer would consult a 300-page manual dating from 1936 that explains the relationships between certain heights and pitches of threads and the lengths and widths of the resulting screws.

FORBES: Magazine Article

Try to imagine the scene at the front of the lines, as already overworked TSA agents are forced to take tape measures or rulers and gauge the length and width of knives, as travelers insist their blades are shorter than 2.36 inches or that they aren't more than a half-inch wide.

CNN: Letting knives on planes would be insane