The rail system is rated at something like 26,000 pounds of trailer.
4 L shaped plates go under the bed an bolt to the top plates sandwiching the bed between them. Those bottom plates go down to the frame an ether bolt or weld to the trucks frame
The hitch I have in the picture is probably rated at about 16,000 pounds so it would break before the plates would come out.
I am only license to drive a single vehicle up to 26,000 pounds an a trailer that is 10,000 pounds or less. I would have to upgrade my license to get anywhere near the limits of that hitch.