A knife, also known as a utility knife, with a replaceable blade used for cutting open boxes.
These types of knives come in two basic forms: a solid blade or a snap(off) blade. The solid blade uses a single solid blade that requires replacing when it become dull. The snap blade design uses a single long segmented blade with which you can snap off the leading end when it dulls to once again have a sharp tip. The blade can then be replaced after you run out of usable segments.
The most common style depicted on Danbooru is the snap blade design; this may be due to the fact that the snap blade design was introduced by a Japanese company in 1956.
