It may be different on yours, but my 94 E320 wagon the two rearward facing third row. The 3rd row seat bottom flips on its rear edge into what I call the grocery hole, the back rest hinges at the base and also fills a shallow hole, making a solid deck to the back of the second row. There are a few ingenious clips & levers that hold it all in, some move sideways. Find a bright flashlight & small mirror, give it a good inspection