The knife is designed for people working in places where cardboard packages are cut: supermarkets, warehouses, on technological lines, etc. The blade, after being ejected and driven into the cardboard, remains in the extended position as a result of friction against the material being cut, while it retracts immediately after losing contact with material to be cut (or when you release the knife from your hand) eliminating the risk of leaving the knife with the blade extended. A multifunctional steel fin allows, for example, cutting packaging tapes without extending the blade or creasing (bending) cardboard boxes. A slider adapted to the shape of the thumb makes it easier to use the knife. The design of the knife allows it to be easily adapted to work for left-handed people.