Editing Utility knife (section)

==== Snap-off utility knife ====
Another type of utility knife is a snap-off utility knife that contains a long, segmented blade that slides out from it. As the endmost edge becomes dull, it can be broken off the remaining blade, exposing the next section, which is sharp and ready for use. The snapping is best accomplished with a blade snapper that is often built-in, or a pair of pliers, and the break occurs at the score lines, where the metal is thinnest. When all of the individual segments are used, the knife may be thrown away, or, more often, refilled with a replacement blade. 

This design was introduced by Japanese manufacturer [[OLFA]] in 1956 as the world's first snap-off blade and was inspired from analyzing the sharp cutting edge produced when glass is broken and how pieces of a chocolate bar break into segments. The sharp cutting edge on these knives is not on the edge where the blade is snapped off; rather one long edge of the whole blade is sharpened, and there are scored diagonal breakoff lines at intervals down the blade. Thus each snapped-off piece is roughly a parallelogram, with each long edge being a breaking edge, and one or both of the short ends being a sharpened edge.