I ran across this today when looking for a parts list for our Dometic refrigerator. We added a shelf in the freezer and needed one little part to act as a sleeve or insert in the wall of the freezer.
With this website, at least with the refrigerators, one needs a Model number (ours is the RM1350) and the Product number (ours is 921148363) and is the four door with water in the door.
You first click on the Model number and then look for your Product number in the list provided. Their parts manual shows the product in the "exploded" view so that you can see where the part belongs. (Sometimes, it is difficult to know what to call the part. (What I would have called an insert, Dometic calls a plug.) Then, there is a corresponding page with the parts list itself.
Hope this is helpful for everyone.
Terry
http://aaarv.net/domre.htm