Fifth-wheel coupling

Ok kiddo, so you know how when you play with your toy cars or trucks, you can attach one car to another one using a little hook thingy? Well, big trucks that transport heavy things have something kind of like that too!

It's called a fifth-wheel coupling, and it's what connects the big trailer (the thing with wheels that carries stuff) to the tractor (the big truck that pulls the trailer).

The fifth-wheel coupling looks like a flat plate with a big hole in the middle, and it sits in the middle of the back of the tractor. There's also a big metal thing that sticks up from the plate, kind of like a pin.

When the driver of the tractor wants to connect the trailer to it, they back the tractor up to the trailer so that the pin fits into the hole in the trailer's kingpin (which is like the hitch on a smaller car). Then they use a lever to bring the plate up and lock it in place around the kingpin so that the trailer can't come off while they're driving.

And there you have it - the fifth-wheel coupling!