A hinged flap including an angled surface and a flat surface prevent the incorrect loading of a 3592 data cartridge into a dedicated pass-through slot. The angled surface of the hinged flap is pushed by a recessed angled surface in the front face of the 3592 data cartridge to force the hinged flap out of the slot, allowing the cartridge to be inserted. In the absence of the recessed angled surface in the front face of the data cartridge, the flat surface of the flap blocks insertion of the data cartridge.