Abstract: The handle has a blade mounting portion with a raised boss forming a slot. The blade has a boss receiving recess with a portion defined by an edge. The cartridge has a transparent top so that the presence of a blade within the cartridge can be observed and an opening at one end into which the blade mounting portion of the handle can be inserted. The bottom of the cartridge includes a spring platform with a recess into which the blade is received. The platform is integral with the cartridge bottom and is mounted in cantilever-like fashion, by a living hinge, to permit it to flex. When the top and bottom of the cartridge are assembled, ribs on the top cause the platform to move to a spring loaded position, where the forward end of the handle boss can enter the blade recess. As the blade mounting portion of the handle is inserted further into the cartridge, the flexibility of the platform permits the boss to be fully seated within the recess, mounting the blade on the handle.