Here's a pic of the old sling, but it will work for illustration. This is not my picture and is copied from a saddle review here. I was lazy about uploading a new pic, sorry.
To the right, you'll see the end of the belt poking out from the metal omni-connector (my made up name for the plates that do everything and that the bridge connects to) and the belt webbing wrapped around a tri glide (thin and black) which keeps the belt ends in place. (the belt is not a continual loop, but just a front piece and the back is the sling)
Choose black coated cast metal slides to get the most out of your belts, collars, and shoulder straps. Adjust webbing or straps with ease using the slides.
www.strapworks.com
I believe that old version was a metal tri glide. Link above is just to a generic tri glide in case it helps for reference.
The new one is similar in that the tri glide keeps the belt attached, but now it is a plastic tri glide. The way it is sewn, if you break the middle piece of plastic on either tri glide on either side of the belt attachment, then your belt is coming off the sling. I fixed this by replacing that piece with an aluminum tri glide made by Cobra that will hold well over 1,000 lbs.
Here's the new sling (you've probably seen).
You can't see the plastic tri glides, but they are there.