Constraint functioning oddly

So I was doing some research on Roblox cart games because I have been wanting to make my own cart system, and while I was testing a Roblox cart game named: cart ride around used car battery, I noticed the carts were very unusual and worked a lot differently but one thing that I struggled to understand was how the wheels were connected to the cart although there wasn’t anything in between them and how only the end of the constraint (which I assume connected the cart to the wheels) was visible so that means that the constraint must have been set to visible if so, how was the rest of the constraint non-visible, and how were the wheels stuck in their place? I tried tackling this problem in Roblox studio but I couldn’t find an answer, I know that this is a cylindrical constraint and I know how they work but this cylindrical constraint doesn’t look like any cylindrical constraint I’ve seen before.
here is the cart upside down


here is the constraint/yellow part when I positioned my camera to enable me to see through the cart
Screenshot 2022-09-06 005751
Thanks for reading, any help would be much appreciated.