A box cutter is a small, handheld, bladed tool, usually with a plastic housing, used to cut corrugated cardboard and packing tape. It is similar to, but not exactly like, a utility knife or Stanley knife. The main difference is that the box cutter will have a single, long blade that is scored in sections along its length. When the top of the blade gets dull, you use a pair of pliers to snap it off and use the fresh razor-sharp section of blade below it.
Because of the thin, strong, and extremely sharp blade, and the excellent, full-hand grip they provide, box cutters slice through cardboard and the strongest reinforced tape like butter. They are frequently used in shipping and receiving departments of retail stores and manufacturing facilities both to open boxes, and to break them down so they can be stored flat. The rest of us will typically get one in a packaged 100-peice tool set.
Safety
A box cutter should always be used razor sharp. They are not designed to be sharpened, rather their extremely cheap, disposable blades are intended to be snapped off and discarded when they start showing signs of wear. A dull knife is a dangerous knife, because it can slip out of the item you wanted to cut and into something you don't want to cut — like, for example, your arm — so don't be stingy discarding worn tips.
When using a box cutter, remember to always cut away from yourself, and away from other people nearby, in case of slippage. The handle is meant to be gripped in the whole hand for maximum leverage. There will be a locking slide adjuster to set the depth of the blade in the side. The segmented blade should only extend one or two segments out from the handle, any more and the blade will be too weak and could snap from lateral pressure. Always set the lock before cutting, and always retract the blade and lock the slider before putting it down or in your pocket between uses. The slider and lock are designed to be easy to adjust and lock one-handed using the thumb.
Cutting a Box
Be careful not to cut too deeply into the box you are opening, or you may damage the items inside. The first way most people try to use a box cutter is to slide it along the tape between the two top flaps of the box. This is effective, but it is also very easy to damage the contents this way. My preferred method is to cut the tape about 1/8 inch (2-3 mm) to the side of the seam, scoring one of the flaps instead of cutting between them. This cuts enough of the tape so that the remaining narrow portion over the seam will pull free easily, while maintaining a protective layer of cardboard between the knife and the contents. You will also need to insert the blade under the flaps to cut the tape free from the sides.
Do not cut here Cut here
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Opening a box
Boxes store much more conveniently when broken down to lie flat. To break down a box with a box cutter, simply flip it over after you have emptied it, and cut the tape on the other side. Since the box is empty at this point, it is often more convenient to cut between the flaps this time. The box will then collapse over on itself at the corners.
Although this works for most box designs, some boxes are not simply folded flaps taped together at the seam. It may be necessary to cut the cardboard itself to break down some boxes, and the box cutter does this almost as easily as cutting tape. As a general rule, you should not have to use a sawing motion to cut through the cardboard, it should slice smoothly through the box material without much resistance. As soon as this is no longer the case, snap off the top segment to expose a fresh, razor-sharp edge.
Weapons
Most tools, when wielded inappropriately, can be weapons. This is especially true of bladed tools, including box cutters. Because they are common tools, they are easy to carry and conceal and do not arouse much suspicion. With the blade retracted, they are safe and convenient to carry in a back pocket or other easily accessible location on one's person. The one-handed operation makes it easy to flick the blade out quickly as an ersatz switchblade.
Although most often used as instruments of vandalism, box cutters were the weapons used in two extremely high-profile attacks in 2001 and 2004.
The more famous, and deadly, of the two was of course the September 11th attacks on New York City and Washington, D.C., in which hijackers reportedly used box cutters to take control of four commercial jets and successfully ram three of them into the Pentagon and the two main towers of the World Trade Center. Approximately 3,000 people were killed.
The other incident was notable and shocking due to the age of the attacker and victim when contrasted with the extreme brutality of the event. On June 1, 2004 an eleven year old girl who has come to be known as Nevada-tan killed a classmate with a box cutter in an empty classroom of their elementary school in Japan. She slit the wrists and throat of the victim and let her bleed to death.
Due to incidents like this, box cutters have started to arouse suspicion when seen in inappropriate settings, such as in airports and schools. They are easy to identify because the plastic handle is typically a bright yellow or orange color. Although a box cutter is a second-rate weapon at best, most people do not walk around armed and are therefore at an extreme disadvantage when confronted with a weapon of any kind.