Containers - Why don't they fall off?

After having watched a number of intermodal double stack trains (at EMY waiting for the Starlate, nee Starlight, and at Horse Shoe Curve) I haven't been able to see anything that holds the top container onto the bottom one. Have I missed something or is it just weight/friction that keeps the top one from falling off?
Appreciate your responses; thanks and best regards,
Rodger

In between the two containers are IBC's or Inter-Box-Connectors. They use the same latching technique that is used on the container trailers.

Since most of the unit is located in the corner columns in the continers above and below... its almost impossible to see these units unless you tresspass into a loading/unloading facility

Did they use the same 'Twistlocks' that are in use on container ships?


The lower container is secured with the well car bottm to prevent moving/sliping, right?

.Taurus. wrote:Did they use the same 'Twistlocks' that are in use on container ships?


The lower container is secured with the well car bottm to prevent moving/sliping, right?

Those would be the same things that are used to hold the two containers together on a train.

And no ... the lower container is not secured ... it just sits in the well. There are protrusions on the floor of the well, that keeps a smaller container from sliding back and forth in the well. If the container isn't placed properly, the container won't sit level and might set off a high car detector if there's another one stacked on top of it. If you hear a car department worker talking on the radio about a container being "up on the pins," that's usually what they're referring to.

.Taurus. wrote:Did they use the same 'Twistlocks' that are in use on container ships?


The lower container is secured with the well car bottm to prevent moving/sliping, right?

Those would be the same things that are used to hold the two containers together on a train.

And no ... the lower container is not secured ... it just sits in the well. There are protrusions on the floor of the well, that keeps a smaller container from sliding back and forth in the well. If the container isn't placed properly, the container won't sit level and might set off a high car detector if there's another one stacked on top of it. If you hear a car department worker talking on the radio about a container being "up on the pins," that's usually what they're referring to.