Recently acquired a lionel flat car with a piggy back trailer chassis and cargo box. FWIW this is an older small size lionel as opposed to scale. Anyway the cargo box is secured to the chassis front and back. Thats good. However the chassis only secures to the flat car in the front. I can see a rectangular slot in the rear of the flat car that might be intended to secure the chassis but there is no corresponding "peg" on the chassis to put in the spot.
Any ideas? Thanks