Abstract: A knife assembly for punching slots on cardboard sheets to allow the subsequent forming of boxes and containers. The knife assembly is substantially a flat arc section with an outer and an inner edge. The outer edge is substantially flat to permit sharp punched edges of the slot. The arc section has two ends and adjacent to one of the ends there is a sharpened section intended to produce a slit termination on the slots punched. The slit can have any desired dimensions including the entire outer edge.