Abstract: A jack-knife is disclosed having a holder and a blade hinged to said holder thus that it can be turned between a closed position in which its cutting edge is in a longitudinal slot of said holder and an opened position which is 180.degree. offset to the closed position and in which the blade can be fixed. The holder of the jack-knife comprises of two joint parts which are injection molded. One of these parts has an integral spring means which acts against a tiltable latch lever. Said lever is pivotable inserted at the back of said holder into the longitudinal slot thereof thus that its latch portion engages a notch in the back of said blade to fix the blade when it is in its opened position. This jack-knife is accordingly composed only of four main parts and can therefore be produced very economically.